Tool MarksTool Marks

• What are tool marks?What are tool marks?• How can tool marks help make a case?How can tool marks help make a case?• If you and I own identical pry bars, how If you and I own identical pry bars, how

can a forensic scientist identify which can a forensic scientist identify which one was used at a crime scene?one was used at a crime scene?

2 Types of Characteristics2 Types of Characteristics

1.1. Class characteristicsClass characteristics1.1. Common to a group of objectsCommon to a group of objects

2.2. Example: A hammer has a distinctive Example: A hammer has a distinctive shape and size.shape and size.

2.2. Individual characteristicsIndividual characteristics1.1. Unique to a given objectUnique to a given object

2.2. Causes?Causes?

3.3. Example: shoesExample: shoes

Types of Tool Mark ImpressionsTypes of Tool Mark Impressions

1.1. Static (“impressed”) marksStatic (“impressed”) marks– Caused by a harder object being Caused by a harder object being

pressed into another softer objectpressed into another softer object– Example: crow bar into woodExample: crow bar into wood

2.2. Dynamic (“striated”) marksDynamic (“striated”) marks– Caused when a tool slides or Caused when a tool slides or

scratches across another surfacescratches across another surface– Example: sliding a key along the side Example: sliding a key along the side

of a car of a car (Locard?)(Locard?)

Types of Tool Mark Types of Tool Mark Impressions, cont…Impressions, cont…

3.3. Cutting (“crushed”) marksCutting (“crushed”) marks– Caused by pressure being applied to Caused by pressure being applied to

both sides of an objectboth sides of an object– Examples: pliers or wire cuttersExamples: pliers or wire cutters

4.4. Multi-stroke marksMulti-stroke marks– Caused by repetitive actionsCaused by repetitive actions– Example: a saw moving back and Example: a saw moving back and

forthforth

Collecting Tool Mark EvidenceCollecting Tool Mark Evidence

• What do you think the FIRST step What do you think the FIRST step would be?would be?

• 22ndnd step: step:– Bagged and taken to lab for further Bagged and taken to lab for further

analysis, if possibleanalysis, if possible– Make a cast of the marks, usually with Make a cast of the marks, usually with

silicone rubber.silicone rubber.

• What do you do with a recovered, What do you do with a recovered, suspect tool?suspect tool?

Examination of a Suspect ToolExamination of a Suspect Tool

• Step 1: ?Step 1: ?• Step 2: ?Step 2: ?• Make test marks with the tool.Make test marks with the tool.• What piece of equipment would you What piece of equipment would you

use to use to comparecompare the marks made in the marks made in the lab with the marks made at the the lab with the marks made at the scene?scene?

• What other evidence can be What other evidence can be obtained from a suspect tool?obtained from a suspect tool?

Case StudyCase Study

• Leah and Milton Rosenthal: Leah and Milton Rosenthal: http://www.channel4.com/science/microsites/S/science/society/forensic_marks.html

• The Lindbergh KidnappingThe Lindbergh Kidnapping

•

March 1March 1,, 1932 1932

• 11stst ransom note, left at the scene: ransom note, left at the scene:Dear Sir, Have $50000 ready, $25000 inDear Sir, Have $50000 ready, $25000 in

$20 bills, $15000 in $10 bills and$20 bills, $15000 in $10 bills and$10000 in $5 bills. After 2-4 days,$10000 in $5 bills. After 2-4 days,we will inform you where to deliverwe will inform you where to deliverthe money.the money.

More Ransom NotesMore Ransom Notes

• March 6March 6th th (postmarked in Brooklyn): increased (postmarked in Brooklyn): increased to $70,000to $70,000

• March 8March 8thth: received by the Lindberghs’ : received by the Lindberghs’ attorney, refusing an intermediary and attorney, refusing an intermediary and requesting a note in the paperrequesting a note in the paper

• Retired principal John Condon printed offer in Retired principal John Condon printed offer in the paper to be the intermediary, and received the paper to be the intermediary, and received an “acceptance” letter on March 9than “acceptance” letter on March 9th

More Ransom NotesMore Ransom Notes

• March 10th: Condon received the ransom money. Negotiations continued through the newspapers.

• March 12th: 5th ransom note delivered by cab driver, stating location of note #6.

More Ransom NotesMore Ransom Notes

• Condon met with “John” in a cemetery to discuss ransom payment, and requested proof od child’s identity.

• March 16th: Note #7 and a baby’s sleeping suit were received by Dr. Condon.

More Ransom NotesMore Ransom Notes

• March 21st: 8th note demands complete compliance; said kidnapping had been planned for a year.

• March 30th: 9th note threatened to increase ransom to $100,000

• April 1st: 10th note said to have money ready the next night

More Ransom NotesMore Ransom Notes

• April 2nd: Taxi driver delivered #11, giving location of #12

• Dr. Condon met with “John” as instructed, handed him the $50,000 ransom, and was told the baby could be found on a boat named “Nellie” near Martha’s Vineyard.

FOUND!!!

• May 12, 1932• Badly decomposed and partially buried,

about 4 ½ miles from home• Death caused by a blow to the head• Had been dead about 2 months

Enter Arthur Koehler, Forest Service

• Identified the types of wood and tool marks on the crudely made ladder