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Tool Marks

Tool Marks. What are tool marks? How can tool marks help make a case? If you and I own identical pry bars, how can a forensic scientist identify which one was used at a crime scene?. 2 Types of Characteristics. Class characteristics Common to a group of objects

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Tool Marks

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  1. Tool Marks What are tool marks? How can tool marks help make a case? If you and I own identical pry bars, how can a forensic scientist identify which one was used at a crime scene?

  2. 2 Types of Characteristics • Class characteristics • Common to a group of objects • Example: A hammer has a distinctive shape and size. • Individual characteristics • Unique to a given object • Causes? • Example: shoes

  3. Types of Tool Mark Impressions • Static (“impressed”) marks • Caused by a harder object being pressed into another softer object • Example: crow bar into wood • Dynamic (“striated”) marks • Caused when a tool slides or scratches across another surface • Example: sliding a key along the side of a car (Locard?)

  4. Types of Tool Mark Impressions, cont… • Cutting (“crushed”) marks • Caused by pressure being applied to both sides of an object • Examples: pliers or wire cutters • Multi-stroke marks • Caused by repetitive actions • Example: a saw moving back and forth

  5. Collecting Tool Mark Evidence • What do you think the FIRST step would be? • 2nd step: • Bagged and taken to lab for further analysis, if possible • Make a cast of the marks, usually with silicone rubber. • What do you do with a recovered, suspect tool?

  6. Examination of a Suspect Tool Step 1: ? Step 2: ? Make test marks with the tool. What piece of equipment would you use to compare the marks made in the lab with the marks made at the scene? What other evidence can be obtained from a suspect tool?

  7. Case Study Leah and Milton Rosenthal: http://www.channel4.com/science/microsites/S/science/society/forensic_marks.html The Lindbergh Kidnapping

  8. March 1, 1932 • 1st ransom note, left at the scene: Dear Sir, Have $50000 ready, $25000 in$20 bills, $15000 in $10 bills and$10000 in $5 bills. After 2-4 days,we will inform you where to deliverthe money.

  9. More Ransom Notes March 6th (postmarked in Brooklyn): increased to $70,000 March 8th: received by the Lindberghs’ attorney, refusing an intermediary and requesting a note in the paper Retired principal John Condon printed offer in the paper to be the intermediary, and received an “acceptance” letter on March 9th

  10. More 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.

  11. More 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.

  12. More 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

  13. More 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.

  14. 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

  15. Enter Arthur Koehler, Forest Service Identified the types of wood and tool marks on the crudely made ladder

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