Lost Tribes of Israel

Student Handout

Did the Dog Do It?

You have been appointed to a jury to determine the guilt of a dog accused of biting a man. The case rests on DNA evidence. It is your responsibility to decide whether the evidence is enough to find the dog guilty.

Procedure

1. Read the evidence you have been given and discuss it as a jury.

2. Consider what other questions you would like to have answered about how DNA fingerprinting works. For example, you might ask:

   • Where in a crime scene might DNA be found?

   • How is a DNA fingerprint made?

   • What probability of DNA match would be considered statistically significant? Is 1 in 10 good enough? 1 in 10,000? 1 in 1 million? 1 in 1 billion?

   • What are some of the problems with DNA fingerprinting?

3. Use additional resources to research answers to your questions.

4. Think about what other questions are important in deciding this case, such as how the evidence was collected and processed and how important the DNA evidence is compared to other evidence in the trial.

5. Based on what you learned from your research and the other issues you have considered, decide as a jury whether you think the accused dog is innocent or guilty. Cite your reasons for your decision when you deliver your verdict.

The Case of the Dog Bite

The Prosecution
Taylor, a 38-year-old man, claims he was bitten by a pit bull named Buddy. He says that Buddy, who lives in Taylor's neighborhood, was loose in the neighborhood and attacked him without any provocation. After being bitten, Taylor claims he cleaned the wound with a towel and then rushed to the hospital. The bite required 10 stitches. Taylor had a local diagnostics laboratory extract DNA from the dog's saliva that was on the towel. DNA fingerprinting showed that five unique markers from the saliva matched markers from Buddy's blood. The odds that the saliva came from a dog other than Buddy are 1 in 350 million. There were no witnesses to the bite.

The Defense
Sam owns the pit bull named Buddy. He says that he always keeps Buddy locked up in the backyard and on a chain. He says he wasn't home the day that Taylor was bitten, but that when he got home that night, Buddy was tied up as usual. No one can verify whether Buddy was in the yard that day. Sam says there are three other pit bulls in the neighborhood and that one of them was the one who bit Taylor. Sam agreed to have Buddy's DNA tested.