- Slides: 16
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 1. Class characteristics 1. Common to a group of objects 2. Example: A hammer has a distinctive shape and size. 2. Individual characteristics 1. 2. 3. Unique to a given object Causes? Example: shoes
Types of Tool Mark Impressions 1. Static (“impressed”) marks – Caused by a harder object being pressed into another softer object – Example: crow bar into wood 2. Dynamic (“striated”) marks – Caused when a tool slides or scratches across another surface – Example: sliding a key along the side of a car (Locard? )
Types of Tool Mark Impressions, cont… 3. Cutting (“crushed”) marks – Caused by pressure being applied to both sides of an object – Examples: pliers or wire cutters 4. Multi-stroke marks – Caused by repetitive actions – Example: a saw moving back and forth
Collecting Tool Mark Evidence • What do you think the FIRST step would be? • 2 nd 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?
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?
Case Study • Leah and Milton Rosenthal: http: //www. channel 4. com/science/m icrosites/S/science/society/forensic _marks. html • The Lindbergh Kidnapping
March 1, 1932 • 1 st 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 deliver the money.
More Ransom Notes • March 6 th (postmarked in Brooklyn): increased to $70, 000 • March 8 th: 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 9 th
More Ransom Notes • March 10 th: Condon received the ransom money. Negotiations continued through the newspapers. • March 12 th: 5 th ransom note delivered by cab driver, stating location of note #6.
More Ransom Notes • Condon met with “John” in a cemetery to discuss ransom payment, and requested proof od child’s identity. • March 16 th: Note #7 and a baby’s sleeping suit were received by Dr. Condon.
More Ransom Notes • March 21 st: 8 th note demands complete compliance; said kidnapping had been planned for a year. • March 30 th: 9 th note threatened to increase ransom to $100, 000 • April 1 st: 10 th note said to have money ready the next night
More Ransom Notes • April 2 nd: 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