field forensic techniques

FIELD FORENSIC TECHNIQUES

Wildlife Crime Scene Management, Processing and Reconstruction

FIRST ON SCENE

• Self Security• Handle any medical emergencies• Call for additional help if necessary• Follow these three steps• 1)Management• Processing• Reconstruction

MANAGEMENT OF CRIME SCENE

• IS SEARCH WARRANT NEEDED?• ESTABLISH SCENE LIMITS• REVIEW SCENE CONTAMINATION OR

ALTERATIONS THAT MAY HAVE ALREADY OCCURRED

• REVIEW EVIDENCE ALREADY COLLECTED• INITIAL WALK THROUGH TO DETERMINE

SCOPE OF THE SCENE

• ASSIGN ROLES AND DUTIES (SECURITY, ENTRY LOGS, DOCUMENTATION, PROCESSING, COLLECTING, PACKAGING, EVIDENCE SECURITY)

• FINAL WALK THROUGH• MAINTAIN AND COORDINATE WITH OTHER

PARTS OF THE INVESTIGATION

PROCESSING A CRIME SCENE

• LOCATION AND ID PHYSICAL EVIDENCE• DOCUMENT THE SCENE (PHOTOGRAPHS)• COLLECT AND PACKAGE EVIDENCE• CLOSE THE SCENE (EXIT PHOTOS)-CONFER

WITH TEAM MEMBERS AND AGREE ALL EVIDENCE HAS BEEN RECOVERED

TYPES OF EVIDENCE

• BIOLOGICAL (BLOOD, HAIR)• PHYSICAL (SHELL CASINGS, PHOTOS, GUNS)• TRACKS (ANIMAL, SHOE PRINT, TIRE PRINT)• GEOLOGICAL (SOIL SAMPLES)• ENTOMOLOGY SAMPLES (INSECTS)• ELECTRONIC (COMPUTERS, CELL PHONES)

DETERMINING TIME OF DEATH IN WILDLIFE

• WHY DO WE NEED TO DETERMINE TIME OF DEATH?

• HOW DO WE DETERMINE TIME OF DEATH?

ITEMS EXAMINED TO DETERMINE TIME OF DEATH

• TEMPERATURE• ELECTRICAL STIMULUS• RIGOR MORTIS• PHYSICAL CHANGES IN THE EYE• CHEMICAL CHANGES IN THE EYE• INSCETS

TEMPERATURE

• After death, the body temperature approaches ambient temperature through loss of heat by radiation, convection and conduction.

Cooling Rate

• Initial body temperature• Air temperature• Body surface area and weight• Handling of carcass after death• Fairly similar for given spp

Initial Body Temperature

• Deer have an average body temperature of 102 degrees

Ambient Temperature

• Air temperature• Estimate daily temperature by averaging

temperature readings at dawn and 3 pm or the previous 12 hours

Determining Body Surface and Weight

• Use chart to determine body weight by measuring girth of chest.

• One chart for live weight • One chart for dressed weight• Difference in buck and doe and fawn (shown

on chart)

LOCATIONS TO TAKE TEMPERATURE

• CENTER OF DEEP MUSCLE (THIGH OF THE HIND QUARTER)

• NASO-PHARYNGEAL CAVITY

CONDITIONS THAT CAN AFFECT COOLING RATE

• DELAYED DRESSING (LITTLE EFFECT ON HEAD BUT DELAYED THIGH TEMPS)

• HEAD COOLS FASTER THAN BODY• CARCASS THAT WAS WASHED WITH COOL

WATER• SKINNING • MOISTURE• WHERE IT IS STORED

DETERMINING TIME OF DEATH FROM TEMPERATURE READINGS

• HAVE TO REFER TO CHARTS• CAN RUN COMPUTER AP TO DETERMINE• KEEP IN MIND THAT THIS IS USED IN

CONJUNCTION WITH OTHER METHODS TO NARROW DOWN THE TIME. IT SHOULD NOT BE USED BY IT’S SELF

ELECTIRCAL STIMULUS

• RESPONSE TO ELECTRICAL STIMULUS IS CHEMICALY RELATED TO THE AMOUNT OF ADENOSINE TRIPHOSPHATE (ATP) IN MUSCLES.

• AFTER DEATH ATP BREAKS DOWN AND RESPONSE TO ELECTIRCAL STIMULUS DECREASES WITH TIME UNTIL NO REPSPONSE IS OBSERVED

FACTORS THAT DETERMINE RESPONSE

• SEVERE DEATH STRUGGLE VS QUICK DEATH• STRESS• FATIGUE• BEST USED TO DETERMINE WITHIN 4 HOURS

OF TOD• DIFFERENT MUSCLE GROUPS GIVE DIFFERENT

RESPONSES

• MUST RELY ON CHARTS FOR ESTIMATING TIME OF DEATH BASED ON RESPONSE TO DIFFERENT MUSCLE GROUPS.

RIGOR MORTIS

• POST MOREM STATE OF RIGITITY WHICH DEVELOPES IN MUSCLE TISSUE WHEN ATP DEPLETES

• DEPENDANT ON PHYSIOLOGICAL AND AMBIENT TEMPERATURE FACTORS

• DIFFERENT JOINTS ARE AFFECTED AT DIFFERENT TIMES

• MULTIPLE JOINTS NEED TO BE CHECKED

JOINTS TO CHECK

• JAW• NECK• WRIST• ANKLE• ELBOW• KNEE

STATE OF RIGOR

• EACH JOINT SHOULD BE CHECKED AND THE STATE OF RIGOR NOTED

• NONE• PARTIAL• FULL

DETERMINING TIME OF DEATH USING RIGOR

• REFER TO CHARTS

TOD BY PHYSICAL CHANGES IN THE EYES

• FOLLOWING DEATH, EYE APPEARANCE CHANGES FROM RIGOR MORTIS OF THE IRIS MUSCLE AND FROM THE LOSS OF TRANSPARENCY AND VOLUME OF THE INTER OCULAR FLUIDS

• RIGOR MORTIS OF THE IRIS MUSCLES CAUSES PUPIL CONSTRICTION (CAN BE MEASURED WITH DIVIDERS OR CALIPERS)

MEASUREMENT OF EYES

• USE EYE WITH GREATEST PUPIL CONSTRICTION

• MEASURE PUPIL DIAMETER VERTICALLY AT RIGHT ANGLES TO THE LONGEST LATERAL DIAMETER

• LATERAL DIAMETER REMAINS CONSTANT• VERTICLE DIAMETER DECREASES WITH TIME• USE CHART TO DETERMINE TOD

ESTIMATING TOD FROM EYE COLOR CHANGES

• FIRST HALF HOUR AFTER DEATH-EYE LENSE AND FLUIDS FULLY TRANSPARENT

• 30 MINUTES TO 6 HOURS AFTER DEATH- LENS AND FLUID REMAIN TRANSPARENT, LUMINOSITY AND COLOR MAY DECREASE SLIGHTLY

• 6 HOURS TO 10 HOURS- COLOR CHANGES TOWARD GREY

• 12 HOURS TO 18 HOURS- COLOR FADES TO DULL GREY, LUMINOSITY FADES AWAY, PUPIL NARROWS TO 1/3 OR LESS OF ORIGINAL DIAMETER

• AFTER 30 HOURS- COLOR AND PUPIL DIAMETER REMAINS THE SAME. HAZY BLUE COLOR APPEARS OVER BROWN COLOR AFTER 48 HOURS

CHEMICAL CHANGES IN THE EYES

• MEASURE POST MORTUM GLUCOSE LEVELS IN THE EYES (NOT AVAILABLE IN FIELD) MUST BE SENT TO LAB AND NOT VERY ECONOMICAL

• WE DON’T USE THIS IN THE FIELD