the influence of limiting instructions on processing and judgments of emotionally evocative evidence

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The Influence of LimitingInstructions on Processing andJudgments of Emotionally EvocativeEvidenceRachel K. Cush a & Jane Goodman Delahunty aa University of New South Wales , AustraliaPublished online: 04 Mar 2011.

To cite this article: Rachel K. Cush & Jane Goodman Delahunty (2006) The Influence ofLimiting Instructions on Processing and Judgments of Emotionally Evocative Evidence,Psychiatry, Psychology and Law, 13:1, 110-123, DOI: 10.1375/pplt.13.1.110

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110 PSYCHIATRY, PSYCHOLOGY AND LAWVOLUME 13 NUMBER 1 2006 pp. 110–123

Correspondence to: Rachel Cush, c/o Jane Goodman-Delahunty, School of Psychology, University of New South Wales, SydneyNSW 2052, Australia. E-mail: [email protected], [email protected]

The Influence of Limiting Instructionson Processing and Judgments of Emotionally Evocative Evidence

Rachel K. Cush and Jane Goodman DelahuntyUniversity of New South Wales, Australia

Most jury instructions are issued after all the evidence has been presented in a trial; however, some are givenduring the trial. When gruesome photographs form part of the evidence in criminal culpability proceedings,the judge will usually instruct jurors to be dispassionate in examining the evidence. This study investigated

whether time of presentation affects the ability of limiting instructions to cure the potentially prejudicial effects ofgruesome photographic evidence by measuring the emotions, cognitions and verdicts of 108 mock jurors in asimulated murder trial. Pre-instructed participants processed evidence in the defendant’s favour and rendered signif-icantly fewer convictions than did post-instructed participants and those who received no limiting instructions.Gruesome photographs did not bias processing of other items in evidence or verdicts, although they elicited signif-icantly greater victim compassion and crime negativity than did neutral photographs. Results suggest that juryinstructions are more conducive to compliance when presented early in the evidence-processing task than whenpresented late.

The Timing of InstructionsThe question of when is the ideal time to presentinstructions to a jury has been prominent in juryresearch for many years. In most jurisdictions,judges direct the jury on matters of law after allthe evidence has been presented, at the end of atrial. Some legal scholars have criticised thispractice and suggest that judges should instructjurors on evidential matters when the evidence ispresented, to enhance comprehension andcompliance (e.g., Frank, 1949; Prettyman, 1960).In support of these contentions are many trialsimulation studies that show that jurors who arepre-instructed about basic legal issues, includingthe presumption of innocence and the burden ofproof, have better recall for probative evidence

(that is, evidence that tends to prove a fact inissue; ForsterLee & Horowitz, 1997; Heuer &Penrod, 1989; Kassin & Wrightsman, 1979) andare more likely to defer their verdict decisionsuntil after all the evidence has been presentedthan post-instructed jurors (Smith, 1991). Thelatter author also found that jurors who were bothpre-instructed and post-instructed were betterable to integrate facts and law.

The value of pre-instruction has been attrib-uted at times to the primacy effect, meaning thatindividuals are better able to recall informationpresented first than information presented last orin the middle (Kassin & Wrightsman, 1979).Another explanation is that pre-instructionprovides a thematic framework or schema that

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LIMITING INSTRUCTIONS AND GRUESOME EVIDENCE

equips jurors better to process trial evidence(ForsterLee & Horowitz, 1997; Pszczynski &Wrightsman, 1981). Source confusion theoryprovides a useful explanation for the relative ineffi-cacy of post-instruction (Wilson & Brekke, 1994).Source confusion occurs when an individualcannot distinguish the separate influences of twoor more sources of a judgment or belief: once ajudgment has been made, the judge cannot retro-spectively dissect the judgment to discoverwhether (or to what extent) it was influenced bycertain information encountered earlier.Consequently, once processing is done, it cannotbe undone (Nisbett & Wilson, 1977; Wegner,Coulton, & Wenzlaff, 1985).

Legal ContextJudges presiding in criminal trials have generaldiscretion to exclude evidence that is unfairlyprejudicial to the defendant (e.g., in Australia,Driscoll v The Queen, 1977; in England, Jeffrey vBlack, 1978; in the United States, United States vMoccia, 1982). The nature of this discretion variesacross jurisdictions: judges in Canada and NewZealand may exclude otherwise admissibleevidence if the prejudicial effect outweighs itsprobative value (e.g., in Canada, R v P (R), 1990;in New Zealand, Jack Taiheke Wyllie v The Queen,2001), whereas judges in England may refuse toallow evidence if its admission would have ‘suchan adverse effect on the fairness of the proceedingsthat the court ought not to admit it’ (s78 of thePolice and Criminal Evidence Act 1984). Thecommon law discretion to exclude unduly preju-dicial evidence was codified in the United Statesby Rule 403 of the Federal Rules of Evidence(1986): ‘Although relevant, evidence may beexcluded if its probative value is substantiallyoutweighed by the danger of unfair prejudice …’

The rule in Australia, section 137 of theEvidence Act 1995 (Cth), overrides the commonlaw discretion to exclude prejudicial evidence incriminal trials: s137 states that evidence must notbe admitted ‘if its probative value is outweighed bythe danger of unfair prejudice to the defendant’.‘Danger of unfair prejudice’ according to theAustralian Law Reform Commission means‘danger that the fact-finder may use the evidenceto make a decision on an improper, perhapsemotional, basis’ (ALRC, 1985, p. 351).Gruesome photographs by their very naturebelong to the category of evidence that puts jurors

in danger of relying improperly on emotion, yetdespite the protection from bias apparentlyafforded by section 137, gruesome photographsare often ruled admissible (e.g., DPP v Weiss,2002; R v Hawkins and Boatswain, 2003). Asimilar situation exists in Canada (e.g., R vMacKay, 2002) and the United States (e.g., Jacobsv Singletary, 1992).

Decisions to admit gruesome photographs aretypically defended by emphasising the probativevalue of photographic evidence: photographs are‘relevant to the proof of … intent’ (R v Telford,1996, p. 435), they assist the jury in ‘relating theevidence to the theory of both the Crown and thedefense [sic]’ (R v Salmon, 1972, p. 185), and they‘make clear to the jury what no amount of the oraldescription can make clear’ (R v P.C. Allen, 1972;cited in R v Bowhay (No. 3), 1998, p. 1). At thesame time, the danger of unfair prejudice isdownplayed: in DPP v Weiss (2002), Cummins Jclaimed that ‘juries demonstrate they cope withphotographs given time’, and in R v Zammit(1999), Wood CJ advised that ‘the sensitivity ofjurors to photographs can too easily be overstated’.These statements reflect a widespread assumptionin western legal systems that because people intoday’s society are continually exposed to imagesof violence in the media, modern juries are notbiased by violence in the way earlier juries mighthave been (e.g., R v Bowhay per Dunford J; R vBaptiste, 2000 per McKinnon J; R v Schaefler,1993 per Chadwick J). The empirical research onthis topic does not support this assumption.

Prejudicial Effects of Emotionally Evocative Evidence

Experimental psychology has shown that exposingmock jurors to emotionally evocative images biaseslegal decisions against the defendant. One trialsimulation study found that when all otherevidence was equal mock jurors exposed to graphicphotographs of a murder victim rendered moreguilty verdicts than those who were not exposed tothe photographs (Douglas, Lyon, & Ogloff,1997). A study investigating the effects of ‘blood-and-guts’ video footage on mock-juror judgmentsrevealed that mock jurors who saw crime scenefootage and believed it was relevant to the case athand defined the threshold burden of proof‘beyond reasonable doubt’ as lower (M = 77%)than both those who believed that the footageportrayed an unrelated crime scene and those who

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RACHEL K. CUSH AND JANE GOODMAN DELAHUNTY

did not see the footage (both Ms = 93%;Kassin & Garfield, 1991). In a simulated murdertrial study involving weak circumstantial evidence,mock jurors who were informed that acts causingdeath were gruesome in nature rendered signifi-cantly more guilty verdicts (34%) than those whowere informed that the acts causing death werenongruesome (14%; Bright & Goodman-Delahunty, 2004).

Bias in Processing and JudgmentJudgments are influenced by many factors: worldknowledge, past experience, personality, mood,time constraints, and so on. We are (usually)aware of the factors that influence our judgments;however, just as we have no privileged access to theprocesses that enable us to see and hear, we oftenhave no direct access to the processes by which ourjudgments are formed (Nisbett & Wilson, 1977;Wilson & Brekke, 1994). This surprising lack ofintrospective awareness was confirmed in asimulated trial study in which mock jurors deniedbeing biased by negative pre-trial publicity aboutthe defendant, yet were more likely to reach aguilty verdict than those exposed to neutralpublicity (Sue, Smith, & Pedroza, 1975).According to an influential model of mentalcontamination, four requirements must be met topreclude biased processing from biasing judgment:(a) awareness that biased processing has occurred,(b) motivation to correct for bias, (c) awareness ofthe direction and magnitude of this bias and (d)the ability to adjust judgments correctly so thatbias is eliminated (Wilson & Brekke, 1994).

Because many effects of emotion are notconsciously accessible, if we are aware at all thatemotion has influenced our cognitions, we generallydo not know the magnitude of this influence(Edwards & Bryan, 1997). Even supposing anindividual were aware of the influence of emotionon his or her reasoning processes, there may be alack of motivation to correct for it because one’sown emotional reactions are generally accepted asan inherently valid and trustworthy source of infor-mation (Clore, 1992; Zajonc, 1980). Combined,these factors suggest that emotion-produced biasesin cognition will almost invariably bias subsequentjudgments. Although at times it may be acceptablefor jurors to use emotion when making sentencingdecisions, the legal system tries to counter theinappropriate effects of potentially prejudicial infor-mation by drawing jurors’ attention to potential

sources of bias and instructing them to eliminatethese sources of bias from their thoughts anddecisions. This approach certainly satisfies the firstof the four conditions for avoiding contaminatedjudgments outlined above but, perhaps inevitably,falls short of the remaining three.

Limiting InstructionsLimiting instructions are directions given by a trialjudge to a jury when information seen or heard byjurors is likely to have a prejudicial impact on theirdecisions. It is assumed that limiting instructions,such as to disregard inadmissible evidence or tolimit the way jurors use admissible evidence, curewhat prejudicial effects evidence might otherwisehave had (see Carter v Kentucky, 1981; R vMacKay, 2002; R v Underwood, 2002). However,as we have seen, having motivation to correct forbias (the second criterion for avoiding mentalcontamination; Wilson & Brekke, 1994) does notensure that correction will occur: a limitinginstruction might draw attention to the possibilitythat jurors’ cognitions have been biased in a partic-ular way (criterion one), but jurors might still notknow the magnitude of the bias (criterion three) ornonetheless be incapable of adjusting a judgmentto remove its influence (criterion four).

A few trial simulation studies have demon-strated that limiting instructions in certaincircumstances had the intended effect on decisionmakers (e.g., Sealy & Cornish, 1973; Simon,1966), but the majority have yielded unfavourableresults (for a review, see Lieberman & Arndt,2000). Although it might seem that issuing alimiting instruction to jurors who have beenexposed to potentially prejudicial evidence is atleast better than nothing, we now know that limit-ing instructions can have the opposite effect tothat intended (Cox & Tanford, 1989; Kramer,Kerr, & Carroll, 1990; Wolf & Montgomery,1977). Limiting instructions may ‘backfire’ eitherbecause jurors are unable or unwilling to comply.In the courtroom, jurors will disobey a limitinginstruction if they perceive it as a threat to theirfreedom to consider all of the available evidence(Brehm, 1966). Jurors endeavouring to complywith an instruction to ignore inadmissibleevidence might nonetheless fail because ofrebounding attempts at thought suppression(Wegner & Erber, 1992). Confounding suchattempts might be the limiting instruction itself,which draws attention to inadmissible evidence,

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increasing its salience in the minds of jurors(Broeder, 1959).

Limited-Use InstructionsAcross jurisdictions, the admission of evidencethat might bias jury decisions is usually accompa-nied by a limiting jury instruction that specifiesthe purposes for which evidence may be used(s136(a) Evidence Act 1995 (Cth); Rule 105 of theFederal Rules of Evidence, 2004; R v Kinkead,1999). According to Canadian case law, limited-use instructions are necessary because juries do not‘know what is and is not a proper use of theevidence absent instruction’ (R v Morehouse, 2004).In a United States murder case, the trial judgecautioned the jury about the graphic content ofphotographic evidence and admonished them toview the photographs dispassionately (UnitedStates v Treas-Wilson, 1993). In England, a rapeconviction was overturned because, among otherthings, the trial judge did not adequately warn thejury that they should not be inflamed by highlyprejudicial evidence presented during the trial (R vAdey, 1998). In an Australian murder trial, thepresiding judge issued this limited-use instructionwhen allowing as evidence a number of photo-graphs depicting the mutilated face of thedeceased:

Members of the jury, the issue in this case … iswhether or not the Crown can prove that theaccused was the perpetrator of the killing andthe robbery, [sic] therefore you should look at thephotographs in a calm deliberate and dispassionatefashion [Italics added]. I have ruled that it isappropriate that you should see these photo-graphs in order that you make the determina-tion in the context of the reality of whathappened, but you should bear in mind that youshouldn’t use any emotion [Italics added] (R vZammit, 1999).

In another Australian murder case, the court ruledthat gruesome photographs should be put beforethe jury because their potentially prejudicialimpact ‘can be appropriately dealt with by instruc-tion’ (R v Kellisar, 1999).

The available evidence suggests that limited-use instructions are ineffectual. In one study,jurors were more likely to convict if they heardevidence about a prior conviction than if they didnot, even when instructed to use the informationto determine credibility, not as an indicator ofguilt (Doob & Kirshenbaum, 1973). A compara-

ble instruction was similarly ineffectual, althoughless so when the previous conviction was for adissimilar crime (Wissler & Saks, 1985). Limited-use instructions in a third study were effective inrelation to prior acquittal evidence but not priorconviction evidence (Green & Dodge, 1995), and,in a simulated civil trial, significantly harsherpenalties were recommended when biasing infor-mation was accompanied by a limited-use instruc-tion (Cox & Tanford, 1989).

An instruction that cautions against emotionalarousal in the face of highly inflammatoryevidence, like the Zammit instruction, raises theconcern that jurors will perceive their emotionalresponses to the evidence as a valid source of infor-mation (Clore, 1992; Zajonc, 1980) and will lackmotivation to comply. On the other hand, ifjurors were motivated to comply, attempts to doso might only be successful in the absence of a‘cognitive load’. In one study, participants whowere not under a cognitive load were able success-fully to comply with instructions to avoidemotion, but participants under a cognitive loadimposed by silent rehearsal of an eight-digitnumber were unable to comply (Wegner, Erber,& Zanakos, 1993). Whether or not motivationand level of cognitive load are factors affectingcompliance with limited-use instructions, thereseems to be no theoretical basis to suggest thatthese factors should affect pre-instructed and post-instructed participants differently. As such, differ-ences in the effects of pre- and post-instructionsshould be attributable to differences in the wayevidence is encoded and processed.

The Timing of Limited-Use InstructionsPre-instructions function as a forewarning aboutthe risk of bias in decision-making. Researchsuggests that without forewarning, individuals areunaware of their own tendency to process newinformation through the distorted lens of prejudice,and that forewarning facilitates strategies to combatbias (Carlson & Russo, 2001). If true, pre-instruc-tion about the risk of bias should have a greaterchance of success than post-instruction. Theevidence regarding the effectiveness of forewarningsis mixed. In some studies, forewarning had little orno ameliorating effects (e.g., Wegner, Coulton, &Wenzlaff, 1985; Wilson, Houston, Etling, &Brekke, 1996); in others, forewarning effectivelyeliminated bias (e.g., Schul, 1993; Weinberg &Baron, 1982). Post-instructions, on the other hand,

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arrive after jurors have encoded the evidence,considered and weighed different versions of events,and possibly made tentative culpability judgments(Pennington & Hastie, 1993). Source confusiontheory suggests that limiting post-instructionsshould be ineffective because cognitive processesonce complete cannot be de-constructed (Wilson &Brekke, 1994). Post-instructed jurors, according tosource confusion theory, should be unable toidentify and remove the biasing influence of preju-dicial evidence and re-construct the story afresh.Simply put, source confusion theory predicts thatlimiting post-instructions will not reduce or elimi-nate bias.

The Present StudyWe expected that participants exposed togruesome photographic evidence would (a)perceive ambiguous evidence as more incriminat-ing, (b) assign more probative weight to incrimi-nating evidence (and less weight to exculpatingevidence) and (c) be more conviction prone thanparticipants exposed to neutral evidence. We alsoanticipated that participants who viewed gruesomeevidence would report (a) more negativity towardthe defendant, (b) more negativity about thecrime, (c) more compassion for the victim and (d)less compassion for the defendant than partici-pants who viewed neutral evidence. The majorpurpose of this study, however, was to examine theeffect of a limited-use instruction, and the conse-quence of varying its timing, on processing andjudgments of gruesome evidence. Rather thanmake specific predictions about the effects oflimiting pre-instructions in the absence of cleartheoretical or empirical guidance, we adopted anattitude of enquiry. In line with source confusiontheory (Wilson & Brekke, 1994), however, weexpected that limiting post-instructions would nothave the intended curative effect. That is, weexpected participants who received post-instruc-tions to exhibit similar results on all measures toparticipants who received no limiting instructions.

MethodParticipants

A total of 108 schoolteachers in Sydney (70females, 38 males) took part in this experiment.Ages ranged from 18 (two were student teach-ers) to 64 years, with a mean age of 46.8 years(SD = 10.04). All participants were eligible forjury duty. All Australian citizens aged 18 or over

who are enrolled to vote, which (with few excep-tions) is compulsory in New South Wales,comprise the pool of eligible jurors (s5 of theJury Act, 1977 (NSW)).

MaterialsParticipants viewed two double-spaced pages ofwritten evidence, three 9 × 13cm colour photo-graphs, and an eight-page questionnaire.

Written EvidenceThe evidence summary was adapted from a NewSouth Wales case in which Johann ‘Ziggy’ Pohlwas wrongfully convicted of his wife’s murder (R vPohl, 1973; as cited in McInerney J, 1992) so thatit was unclear whether the defendant was theperpetrator. A pilot test with 78 undergraduatesattending a Foundations of Law class confirmedthe ambiguity of the written evidence: 59% ofparticipants found the defendant guilty; 41%found him not guilty. Pilot testing also confirmedwhich items in the evidence summary wereperceived as inculpatory, exculpatory and ambigu-ous.

Photographic EvidenceFour photographic exhibits separately depicted asmiling young woman, the disturbed interior of ahouse, the disfigured face and torso of a murdervictim, and the front door to a house. A manipu-lation check with 78 undergraduates (after pilottesting the written evidence) established theemotionally evocative qualities of the photo-graphs. On a scale from 0 (not at all) to 8(extremely), participants rated the extent to whicheach photograph induced anger, panic, disgust,anxiety, fear, horror, annoyance and distress. Acomposite negative emotion measure was calcu-lated by averaging the eight emotion scores(Cronbach’s alpha = .97; N = 8). A one-wayANOVA confirmed that the photographs differedsignificantly in their evocation of negativeemotion, F(3, 260) = 219.49, p < .0005. Follow-up orthogonal contrasts revealed no differencebetween the photographs of the smiling woman(M = 0.8; SD = 1.36) and the door (M = 0.5;SD = 0.95), F(3, 260) = 1.42, p = .23; d = 0.26.The disturbed-interior photograph (M = 3.4; SD =1.79) was significantly more evocative than bothof these (combined M = 0.6; SD = 1.18),F(3, 260) = 164.58, p < .0005; d = 1.85, and thegruesome photograph (M = 6.0; SD = 1.47)

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evoked significantly more negative emotion thanthe first three (combined M = 1.6; SD = 1.92),F(3, 260) = 492.44, p < .0005; d = 2.57.

Limiting Instruction

Minor changes to the wording of the jurydirection cited in R v Zammit (1999) rendered itappropriate as both a pre- and post-instruction forthe present task without altering its substance. Theinstruction given in this study was:

You should consider the photographs in a calmdeliberate and dispassionate fashion. It is appro-priate that you should see these photographs inorder that you answer the questions in thecontext of the reality of what happened, butyou should bear in mind that you shouldn’t useany emotion.

Dependent Measures

Self-reported emotional responses. Participantsrated from 0 (not at all) to 8 (extremely) the extentof their feelings towards the defendant and thevictim in terms of anger, sympathy, contempt,pity, disgust and sadness, and the extent of theirfeelings about the crime in terms of horror, satis-faction, sadness, apathy, disgust, calmness andanger. Calmness, satisfaction and apathy in relationto the crime, and anger, contempt and disgust inrelation to the victim, were included to encouragethoughtfulness about each item.

Probative value of the evidence. In the first ofthis two-part section, participants indicated from–4 (much less likely) to +4 (much more likely) theextent to which nine ambiguous facts in evidenceimplied factual guilt. In the second part, partici-pants were allocated 100 points to be dividedbetween 10 key facts in evidence, five of whichwere incriminating and five exculpating, with themost points to be assigned to the facts regarded byparticipants as most important.

Verdict. Participants judged whether the defen-dant was guilty or not guilty in fact.

Self-monitoring of bias. Participants indicatedwhether they relied on emotion when makingtheir culpability decision. Because of the dangerthat demand characteristics would deter partici-pants from answering honestly, the questionnairefirst informed participants that this instruction

had been issued to the jury in the trial from whichthe facts were taken.

QuestionnaireTo check for order effects, the order of questionswas counterbalanced within experimental groupsso that half of the participants answered verdictitems before answering probative value of theevidence items and vice versa (groups one and two,respectively). No differences between groups oneand two were found: conviction rates were 62%and 58% for groups one and two, respectively,χ2(1, N = 106) = 0.15, p = .70; mean inculpatoryvalues assigned to ambiguous evidence were 5.5and 5.8, respectively (SDs = 1.20 and 1.39), t(106)= –0.92, p = .36, two-tailed; and mean probativeweights assigned to incriminating evidence were56.6 and 59.7, respectively (SDs = 27.71 and18.62), t(106) = –0.67, p = .51.

DesignA 2 (photograph: gruesome/neutral) × 3 (instruc-tion: pre/post/none) between-groups design wasused. All participants, who were randomlyallocated to one of the six experimental groups,viewed three photographs: two were identicalacross groups (the smiling woman and the disar-rayed house) and the third photograph varied.One half of the participants viewed an image of adisfigured murder victim (gruesome); the remain-der viewed an image of a door (neutral).Participants in the pre- and post-instructiongroups (but not participants in the no-instructiongroup) received the limiting instruction presentedabove; it was inserted before the written evidencein the pre-instruction condition and before thefirst questionnaire item in the post-instructioncondition.

ProcedureSurveys were mailed to participants, whocompleted the task individually, in their own time.Written instructions advised that the purpose ofthe study was to investigate the mental processes ofjurors and that participation involved reading thefacts in a criminal case, looking at photographicevidence admitted during the trial, and answeringsome questions. Warning was given that someparticipants might find the evidence gruesome anddistressing. Participants examined the writtenevidence and photographic exhibits until ready toproceed. For the purpose of isolating the effects of

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the pre- and post-instructions, participants wereasked not to look back at the evidence once theycommenced the questionnaire.1

ResultsSelf-Reported Emotional Responses

to the EvidenceEmotions Towards the Victim and DefendantThe variables measuring emotions evoked by thevictim and the defendant (excluding the threefiller items) were subjected to an exploratory factoranalysis. The nine variables loaded strongly ontothree components that account for 78.9% of thevariance: defendant negativity (anger, disgust andcontempt in relation to the defendant), defendantcompassion (sympathy, pity and sadness in relationto the defendant) and victim compassion (sympa-thy, pity and sadness in relation to the victim).Table 1 shows the mean and standard deviationscores on these components for each experimentalgroup. An overall ANOVA revealed a significantmain effect of photographic evidence on victimcompassion, but no significant interaction or maineffect of limiting instruction. As expected, partici-pants who viewed gruesome evidence reportedsignificantly more compassion for the victim(M = 6.7; SD = 1.56) than participants who didnot view this evidence (M = 5.7; SD = 2.18),F(1, 102) = 7.48, p < .01; d = 0.53.

An overall ANOVA showed, contrary toexpectations, that experimental manipulation ofphotographic evidence and the limiting instruc-tion did not significantly affect defendant negativ-ity. A near-significant interaction of photographic

evidence and limiting instruction on defendantcompassion emerged, F(2, 102) = 2.90, p = .06.This interaction suggests that among pre-instructed participants there was a tendency forthose who viewed gruesome evidence to reportmore defendant compassion than those whoviewed neutral evidence, and among the remain-ing participants, there was a tendency for thosewho viewed gruesome evidence to report lessdefendant compassion than those who viewedneutral evidence.

Emotions in Response to the CrimeAn exploratory factor analysis of the variablesmeasuring emotion in relation to the crime(excluding the three filler items) found that allfour (anger, horror, disgust and sadness) loadedstrongly onto a single component (event negativity)that explains 55% of the variance. Table 1 showsmeans and standard deviations on this componentfor each experimental group. An overall ANOVArevealed that event negativity was significantlyaffected by photographic evidence, F(1, 100) =21.25, p < .0005; the limiting instruction, F(2,100) = 4.85, p = .01; and an interaction of the two,F(2, 100) = 3.36, p < .05. The main effect ofphotographic evidence indicates that more eventnegativity was reported by participants whoviewed gruesome evidence (M = 5.9; SD = 1.65)than by participants who viewed neutral evidence(M = 4.4; SD = 1.93), F(1, 100) = 21.25, p <.0005; d = 0.84, regardless of limiting instruction.Post-hoc comparisons revealed that pre-instructedparticipants reported significantly less eventnegativity (M = 4.6; SD = 2.04) than participants

Table 1

Mean Defendant, Victim and Event Emotions by Experimental Group (With Standard Deviations in Parentheses)


Emotions Photograph Pre Post None

Defendant Negativity Gruesome 1.6 (1.94) 1.9 (2.44) 2.5 (2.52)Neutral 2.7 (2.66) 1.9 (1.88) 1.8 (1.76)

Defendant Compassion Gruesome 3.5 (2.01) 2.4 (2.03) 2.6 (2.07)Neutral 2.3 (1.78) 2.9 (1.65) 3.5 (1.56)

Victim Compassion Gruesome 6.2 (1.59) 6.8 (1.42) 7.1 (1.60)Neutral 5.5 (2.21) 5.7 (2.12) 5.7 (2.18)

Event Negativity Gruesome 5.8 (1.52) 5.2 (1.79) 6.6 (1.32)Neutral 3.3 (1.79) 4.8 (2.07) 4.9 (1.61)

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who received no limiting instruction (M = 5.7;SD = 1.70), HSD = 1.11, p < .05; d = 0.59. Noother comparison was significant. Simple effectstests of the interaction showed that more eventnegativity was reported by participants whoviewed gruesome versus neutral evidence if limit-ing pre-instructions, F(1, 31) = 18.15, p < .0005;d = 1.51, or no instructions, F(1, 35) = 12.92, p =.001; d = 1.15, were given, but there was no signif-icant difference between gruesome and neutralgroups when post-instructions were given,F(1, 34) = 0.34, p = .57.

Processing of the EvidenceInculpatory Value of Ambiguous EvidenceFor ease of interpretation, ratings of the tendencyof nine ambiguous facts in evidence to imply guiltor innocence were recoded so that scores rangedfrom 1 to 9. Scores above 5 indicate that itemswere perceived as inculpatory; scores below 5indicate that items were perceived as exculpatory.Because of the strong inter-correlations among thenine items, scores were averaged to provide a singlemeasure of inculpatory value assigned to ambigu-ous evidence (Cronbach’s alpha = .90; N = 9).Table 2 shows mean inculpatory value scores byexperimental group. It was predicted thatgruesome evidence would increase the inculpatoryvalue assigned to ambiguous informationcompared to neutral evidence. An overall ANOVAfound no significant main effect of limitinginstruction on inculpatory value assigned to

ambiguous information, but it revealed a near-significant main effect of photographic evidence —in the opposite-to-predicted direction, F(1, 102) =3.86, p = .052; d = –0.39 — and a significant inter-action effect, F(2, 102) = 3.61, p < .05. Simpleeffects tests showed, rather surprisingly, that pre-instructed participants perceived ambiguous infor-mation as less incriminating if they viewed agruesome photograph than if they viewed a neutralphotograph, F(1, 33) = 8.57, p < .01; d = 0.99.Figure 1 illustrates this pattern of results. There wasno photographic evidence effect for participantswho received post-instructions, F(1, 34) = 0.07,p = .79, or no instructions, F(1, 35) = .09, p = .77.

Probative Weight of Incriminating and Exculpating EvidenceBecause the total probative weight assigned byparticipants to five incriminating and five excul-pating facts summed to 100, a composite probativeweight indicator was computed from the relativesum of weights assigned to each category. SeeTable 2 for mean probative weight scores byexperimental group. Though it was predicted thatgruesome evidence would increase the probative

Table 2

Mean Probative Value Assigned to Ambiguous andIncriminating Evidence by Experimental Group (WithStandard Deviations in Parentheses)


Photograph Pre Post None

Inculpatory value assigned to ambiguous evidencea

Gruesome 5.0 (0.78) 5.5 (1.05) 5.7 (1.03)Neutral 6.4 (1.84) 5.4 (1.01) 5.8 (1.51)

Probative weight assigned to incriminating evidenceb

Gruesome 48.1 (24.60) 60.6 (23.24) 59.6 (26.85)Neutral 48.7 (22.29) 64.6 (25.33) 65.4 (17.85)

Note: aScores above 5 indicate that ambiguous evidence was perceived asinculpatory; scores below 5 indicate that ambiguous evidence wasperceived as exculpatory.bFor each group, the mean probative weight assigned to exculpatingevidence is inversely proportional to the mean shown.

Figure 1

Mean inculpatory value assigned to ambiguous informa-tion by gruesome and neutral photograph groups underdifferent limiting instruction conditions.Note: Scores above 5 indicate that evidence was perceived as inculpatory;

scores below 5 indicae that evidence was perceived as exculpatory.

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weight assigned to incriminating evidence (anddecrease weight assigned to exculpating evidence),an overall ANOVA found that probative weightshifted only as a function of the level of limitinginstruction given, F(2, 102) = 4.26, p < .05, not asa function of photographic evidence, F(1, 102) =0.59, p = .45, or an interaction between the two,F(2, 102) = 0.11, p = .89. Figure 2 shows the meanprobative weight scores for each limiting instruc-tion condition. Follow-up orthogonal contrastsshowed that participants who received pre-instruc-tions assigned significantly less probative weight toincriminating evidence (M = 48.4; SD = 23.16)than participants who did not receive pre-instruc-tions (both Ms = 62.6; combined SD = 23.11),p < .005; d = –0.61. No difference in the probativeweight assigned to incriminating evidence wasapparent between participants who received post-instructions (M = 62.6; SD = 23.99) and noinstructions (M = 62.6; SD = 22.55), p = .99.

JudgmentsConsistent with the conviction rate obtained inthe pilot test, more than half of the participants(60%) indicated that the defendant was guilty.Table 3 shows conviction rates by experimentalgroup. A logistic regression determined whether

the gruesome evidence and the limiting instructionaffected verdict choices of participants. Overall, theexperimental manipulations did not significantlyaffect verdict choice, χ2(3, N = 106) = 5.71, p = .13.Conviction rates for participants who viewedgruesome and neutral evidence (58% and 62%,respectively) were not significantly different, χ2(1,N = 106) = 0.17, p = .69. However, it emerged thatwhen photographic evidence was disregarded, theconviction rate was significantly lower amongparticipants who received pre-instructions (44%)than among participants who did not, 68%; χ2(1,N = 106) = 5.39, p = .02. There was no differencebetween participants who received post-instruc-tions (67%) and participants who received nolimiting instructions, 69%; χ2(1, N = 106) = 0.06,p = .80.

Self-Monitoring of BiasMost participants asserted that they did not relyon emotion when making a culpability decision(86%). A similar proportion of participants in thegruesome (84%) and neutral evidence (89%)conditions, and in the pre-instruction (85%),post-instruction (88%) and no-instruction (86%)conditions expressed this opinion.

DiscussionEffects of Exposure to Gruesome Evidence

Processing and Judgments of the EvidenceGuided by findings in recent jury studies thatexposure to gruesome evidence biases processing offactual evidence and increases convictions (Bright &Goodman-Delahunty, 2004; Douglas et al., 1997),we expected that gruesome photographic evidencewould (a) increase the perceived inculpatory value ofambiguous evidence, (b) increase the probativeweight assigned to incriminating evidence (anddecrease the probative weight assigned to exculpat-

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Figure 2

Mean probative weight assigned to incriminating andexculpating evidence under different limiting instructionconditions.

Table 3

Percentage of Convictions in Gruesome and NeutralEvidence Groups Under Different Instruction Conditions


Photograph Pre Post None

Gruesome 35 72 67Neutral 53 61 72Overall 44 67 69

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ing evidence) and (c) increase convictions comparedto neutral evidence. Results do not bear out thesepredictions; however, it is doubtful, considering theweight of empirical support for the biasing effects ofgruesome evidence (Bright & Goodman-Delahunty,2004; Douglas et al., 1997; Kassin & Garfield, 1991;Oliver & Griffitt, 1976; Whalen & Blanchard,1982), that there was no gruesome evidence effect todetect. Rather, we suggest that the deviation ofpresent findings from previous findings is theproduct of methodological differences.

The most notable variation in methodology isthe length and complexity of the written evidence:Douglas et al. (1997) used 30 single-spaced pages,Bright and Goodman-Delahunty (2004) used 12double-spaced pages, and this study used 2 double-spaced pages and presented the evidence as ‘knownfacts’ rather than controverted statements within atrial transcript. It is likely that the processingrequired for two pages of known facts was not suffi-ciently prolonged or elaborate to enable gruesomephotographs to have a biasing influence (see Forgas,1995). This speculation is supported by social cogni-tion research showing that more-prolonged andelaborate processing increases the influence ofemotion on judgments (for a review, see Forgas,1995). A second point of difference is that Brightand Goodman-Delahunty (2004) provided a writtendescription of gruesome conduct, whereas this studypresented a photographic depiction of gruesomeconsequences. It is possible that the different present-ing media induced different emotions with distincteffects on processing (see DeSteno, Petty, Rucker,Wegener, & Braverman, 2004).

Emotional Responses to the EvidenceJury researchers have speculated that emotionmediates the prejudicial effects of gruesomeevidence on judgment (Oliver & Griffitt, 1976;Wilson & Blanchard, 1982). We expectedgruesome evidence to be more emotionally arous-ing than neutral evidence. As predicted, gruesomephotographs increased victim compassion andratings of event negativity, but contrary to predic-tions, gruesome photographs did not significantlyincrease defendant negativity or decrease defendantcompassion compared to neutral evidence. Thelikely reason is that the emotions aroused bygruesome evidence were more readily associatedwith the victim and the crime but were less clearlyassociated with a defendant whose culpability wasin doubt.

Limiting InstructionsThe Pre-Instruction EffectIn several studies, mock jurors exposed to prejudicialevidence delivered judgments biased against thedefendant yet denied that emotion had influencedtheir decisions (e.g., Douglas et al., 1997; Sue et al.,1975). On this basis, Douglas et al. speculated thatjurors would be incapable of complying with direc-tions to avoid relying on emotion when consideringgruesome evidence. The present results, while repli-cating these self-reported findings (86% of partici-pants asserted that they did not use emotion), do notsupport this speculation. Rather, the processing andjudgments of participants who received limiting pre-instructions were significantly different to those ofparticipants who did not receive pre-instructions (the‘pre-instruction effect’). Disregarding photographicevidence, pre-instructions reduced event negativity(see Table 1) compared to no instructions, andreduced probative weight assigned to incriminatingevidence (see Figure 2) and conviction rates (seeTable 3) compared to post-instructions or noinstructions. Further, photographic evidence signifi-cantly affected inculpatory values assigned to theevidence only when pre-instructions were given (seeFigure 1).

Demand characteristics might be partiallyresponsible for the striking persistence of the pre-instruction effect: participants may have striven forinternal consistency in their responses or attemptedto justify one response by making another (see Frey,1982). For instance, after reaching a verdict, partici-pants might have endeavoured to ‘feel’ the right wayabout the defendant or to ‘perceive’ the evidenceappropriately. This rendering, though it helpsexplain the consistency of the pre-instruction effectacross measures, does not explain its initial appear-ance. As such, we propose the following account,which applies the four-criterion mental contamina-tion model (Wilson & Brekke, 1994) to the mockjuror’s decision task. The Zammit instruction, whenissued prior to presentation of the evidence, drewattention to the potentially prejudicial effects ofemotionally evocative evidence (thereby fulfillingcriterion one; Wilson & Brekke, 1994). However,the instruction, though it implied the direction thisbias would take, did not convey its expected magni-tude (criterion three). Aware of the prejudicial effectsof the gruesome evidence, participants tried tocorrect the bias by adjusting their judgments in theopposite direction. Alas, they miscalculated the

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magnitude of correction required (criterion four),overcorrected and rendered a decision more biasedin favour of the defendant.

The Post-Instruction EffectConsistent with a source confusion hypothesis(Wilson & Brekke, 1994), results suggest thatpost-instructions were ineffective. That is,responses to post-instructions resembled responsesin the absence of limiting instructions acrossmeasures including defendant and victimemotions (see Table 1), inculpatory value assignedto ambiguous evidence (see Table 2), probativeweight assigned to incriminating and exculpatingevidence (see Figure 2) and verdict choice (seeTable 3). These results suggest that participantswho received limiting post-instructions wereunable to re-examine their cognitions, remove the(alleged) influence of emotion and re-constructthe story afresh (see Pennington & Hastie, 1993).Whereas pre-instructions function as a forewarn-ing about the potential for bias and allow forattempts to avoid or correct bias (Carlson &Russo, 2001), post-instructions arrive afterevidence has been encoded, weighed and perhapseven judged, when jurors are impotent to removethe influence of emotions that have infusedprocessing from the very outset (cf. criterion four;Wilson & Brekke, 1994). Other accounts of thenull post-instruction effect are unconvincing inlight of the effectiveness (or over-effectiveness) ofthe pre-instruction. A reactance explanation is notplausible because there seems no reason why limit-ing post-instructions should be more threateningthan limiting pre-instructions (see Brehm, 1966),and self reports indicate that most post-instructedparticipants were compliant with instructions(88%). A mental control hypothesis is not consis-tent with present findings because the cognitiveload borne by post-instructed participants wasidentical to the load borne by pre-instructedparticipants. As such, attempts to suppressemotion should have been unaffected by thetiming of instructions (see Wegner, Erber, &Zanakos, 1993).

Methodological LimitationsThe present experimental task diverged from thetask of an actual juror in several important ways:first, sensory aspects such as seeing and hearingwitnesses were missing, as were real-world conse-quences for a defendant or victim and the sense of

accountability that would undoubtedly accom-pany a jury verdict; second, participants did notconfer with each other as jurors do before deliver-ing a verdict; and third, the cognitive processesrequired for two pages of known facts would beless prolonged and elaborate than those requiredin an actual trial, and would be less likely to exposeprocessing of other facts in evidence to the biasingeffects of gruesome photographs (see Forgas,1995). Written evidence conveyed through alengthier trial transcript of controverted evidencemight enable the emotions aroused by gruesomephotographs to affect processing, for instance, byenhancing the persuasiveness of the prosecution’scase (DeSteno et al., 2004) or informingjudgments of witness credibility (Semmler &Brewer, 2002; Schwartz & Clore, 1988).

For theoretical purposes, and for the purposeof investigating juror (as opposed to jury) decisionprocesses, the absence of mock jury deliberationsin our study is probably not damaging. Studiesinvestigating the effects of deliberations on mockjurors’ propensity to comply with instructions toignore inadmissible evidence have yielded mixedresults (although different researchers have studieddifferent types of instructions; see Lieberman &Arndt, 2000). Some have shown that deliberationsreduce the biasing influence of inadmissible infor-mation (e.g., London & Nunez, 2000), whereasothers have found that deliberations are ineffectual(e.g., Kramer et al., 1990). To our knowledge, noresearch has investigated whether deliberationsimprove jurors’ compliance with limited-useinstructions. As such, we can only conjectureabout whether deliberations might have affectedresponses in this study.

Another limitation is that the present studyrelied on self-reports of emotional reactions to theevidence and use of emotion when making a culpa-bility decision. Despite preventative measures,demand characteristics might have influencedresponses to these items. That is, participants mighthave tried to be ‘good’ subjects by reporting appar-ently appropriate emotional responses to theevidence and indicating compliance with the limit-ing instruction. Future researchers can avoid thisproblem by manipulating emotional states experi-mentally and incorporating other measures ofarousal (e.g., physiological indicators).

Finally, it can be argued that our sample didnot adequately resemble the actual pool of poten-tial jurors because the participants are members

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of a profession and are likely better educated thanthe average juror. However, many trial simula-tion studies rely on undergraduates whose lifeexperience, educational and cultural background,and age range are far more restricted than theteachers who participated in this study and lessclosely resemble those of average jurors.

ApplicationsIn the absence of the predicted gruesome evidenceeffect, it is difficult to evaluate the significance ofour finding that limiting pre-instructionsproduced a pro-defense bias. Had the gruesomeevidence affected processing as expected, adjust-ments for bias may have been accurate and subse-quent responses unbiased. Replicating this studywith more elaborate materials should resolve thismatter. The more important outcome is that pre-instructions significantly impacted processing andjudgments whereas post-instructions did not. Thisfinding suggests that limiting pre-instructionsinvoked the use of strategies to avoid bias thatpost-instructions did not. Applied to the court-room, these results imply that jurors activelyengage with information at the encoding stage,which is when they are able (and willing) to imple-ment strategies to comply with judicial directions.As such, limiting instructions should be mosteffective when issued prior to presentation oflimited-use evidence. Consistent with this propo-sition are many studies showing that jurors’memory for instructions and evidence, and theirability to apply the law to the evidence, isimproved when jury directions are given at thestart of the trial (ForsterLee & Horowitz, 1997;Heuer & Penrod, 1989; Kassin & Wrightsman,1979). These findings, together with thosereported in the present study, suggest that the legalsystem will benefit from recognising in all itsprocedures that jurors are active processors ofinformation who are better equipped to applyinstructions to the evidence prospectively thanretrospectively.

Endnote1 This procedure does not necessarily reflect current

practise in New South Wales: subject to the judge’sdiscretion to exclude from the jury room ‘exhibitsof a highly inflammatory or prejudicial character’(Kozul v The Queen (1981) para. 224 per StephenJ), the jury is permitted to take photographicexhibits into the jury room when they retire to

consider their verdict (New South Wales LawReform Commission Report 48 (1986), chapter 6;see also s55A of the Jury Act 1977 (NSW)).

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the influence of limiting instructions on processing and judgments of emotionally evocative evidence

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