DNA testing and DNA evidence are important to the investigation and solving of crimes including murder and rape. However, the scientific process is complicated, and the presentation of DNA evidence must focus on the best way to help the jury understand. Prosecutors must be prepared to use an expert in the field who can explain what DNA is, why it was collected, and what was discovered. Criminal lawyers who defend clients must be well-versed in the how DNA is found, collected, and presented in court at trial so that they can do their best job providing an excellent defense for their client.

DNA evidence can be used to identify the offender, eliminate or confirm a suspect, or to exonerate someone wrongly convicted of a crime. Criminal lawyers know that DNA evidence can be highly accurate, but there are inherent problems including laboratory errors, collection mistakes or mishandling of DNA evidence, or even overzealous investigators or prosecutors who are accused of planting DNA evidence, such as in the O.J. Simpson case. These problems open the door for the criminal lawyer to effectively defend against DNA evidence presented at trial.

To present DNA evidence effectively in court, prosecutors must be able to establish the chain of custody from collection to laboratory testing. Criminal lawyers will be looking at each step along the way to find the basis for their defense. DNA evidence can be collected from saliva, blood, skin tissue, hair, bones, and bodily secretions. It can be found on victims or their clothing, carpets, bedding—anywhere in the crime scene. But DNA evidence can be easily contaminated if not collected properly. Criminal lawyers can use this possibility as a way to sway the opinion of the jury at trial.