One of the scariest things you can probably hear if you're facing criminal charges is a detective saying that they have physical evidence that you were at a crime scene -- especially if you weren't. Juries these days love forensic evidence, in part because of the CSI effect. Popular television has many people convinced that forensic evidence is easy and foolproof, when it is not. If you're facing forensic evidence in your criminal trial, don't assume that you're as good as convicted. There are many ways to show the jury that forensic evidence isn't as solid as they might believe.

Is this really forensic evidence or junk science?

Some types of forensic evidence have a long history of use in the courtrooms -- despite the fact that there may be little to no basis to actually consider the evidence scientific in nature. In some cases, there may be a possibility that the science is valid, but the results rely so heavily on the skill and interpretation of the forensic examiner that it can be hard to tell when you are getting credible results and when you aren't.

For example, studies going back more than five years indicate that bite-mark analysis has questionable forensic value. Teeth don't make neat impressions in every surface, the way that they do when a defendant is asked to bite down on dental putty to provide dental impressions for comparison. Movement and pressure can alter the appearance of bite marks quite a bit. Unless you have exceptionally unique dental impressions, bite-mark evidence can often be successfully challenged based on studies that show its unreliability. At least a dozen people who were charged or convicted of crimes based on bite-mark evidence have been exonerated in the last ten years.

Hair analysis is another questionable forensic tool. It is sometimes useful for mitochondrial DNA extraction. However, much of the time, hair analysis is done by microscopic comparison between hair found at the crime scene and hair collected from the suspect. A recent study of expert testimony given by examiners trained by the FBI indicates that at least 90% of their cases contained analysis errors.

Reports like these illustrate how your attorney can often challenge physical evidence that many people erroneously believe is ironclad.

Are the lab and the analyst really qualified?

Your attorney will also be able to delve into other issues that can lead to doubts about the quality of any forensic expert testimony:

• What is the analyst's background? How long has he or she been working as an expert? Does he or she work exclusively for the prosecution?
• What is the lab's background and reputation? Does it have a history of flawed reports? What are the quality controls in the lab?
• What was the chain of custody for the evidence? Who handled it and when? Is every transition between individuals and rooms documented? Was the evidence ever accidentally exposed to contaminants?

Don't allow yourself to be intimidated by the idea that there is forensic evidence against you. Forensic evidence is often only as good as the jury is willing to believe it is, and your attorney can often find ways to make them question its validity. For more information about criminal defense, contact a law office, such as Walsh Fewkes Sterba.