Imagine that you are called to provide expert witness testimony in the following case:?

Question

A neighbor's dog was killed last week. Apparently, someone opened your neighbor's fence and hit the dog with a blunt object. An anonymous witness gave the name of a sullen teenager who lives a few blocks away. However, the teen will not admit to the vicious act and the only evidence that connects the teen to the crime is a brownish stain on his sneakers that appears to be blood. You are called to testify that the brownish stain is blood from the dog that you have matched to blood found at the scene. Discuss what you would need to cover in your testimony to convince a jury to listen to you.

Answer 1

You need testimony that A took blood from the particular dog; That A placed it in a secure container (like a test tube) & sealed it in a secure fashion & placed it in (somewhere); That B took the container from (same somewhere); broke the unopened seal; removed the blood & performed a particular test (must describe the test) that will identify the blood type and that the result was type (Dog type X). Then you need the same chain of testimony that the same thing was done with a sample from the kid's sneakers. Then B (or some other expert) must state that the blood type was (Dog typ X). Then someone familiar with the scientific facts must testify that x% of dogs have this same blood type. Note: this only rules out other types; it is not conclusive. Only DNA is. You can do the same thing for DNA except you don't test for type but extract DNA & then do a match. It takes a couple of weeks & costs a LOT more, assuming the sample on the kid's sneakers is usable.

Answer 2

I would need to present my qualifications to be an expert in this field. Usually expert witnesses provide attorneys with a CV which lists their education, job experience, papers/books they have written, and anything else that would qualify this person as an "expert" in the field.

Once my qualifications were entered into evidence, I would then need to detail how the scientific tests were performed. This would mean educating the jury as to how this test became a standard in the scientific community, the percentage of times that this test is correct, how the correctness of this test is evaluated, which scientific group supports this test.

Next I would speak about this specific test. Talk about how the blood was collected from the dog and the collection of the brown substance from the teen. As an expert I would not talk about the 'dog blood' and the 'stain on the teen's pants' but call it Sample A and Sample B in order to be as objective as possible. I would report on the chain of evidence - which is who had control of the two samples from the day it was taken until today. This establishes that there was no tampering. I would describe how the test links these two samples on a scientific basis. The facts of the test should prove the conclusion.

Answer 3

I suggest you read the Federal Rules of Evidence 901(a) and 901(b).