As this blog has discussed in previous posts, by driving in the state of Wisconsin you have given implied consent for your blood, breath or urine to be collected for purposes of alcohol and drug testing in the event that you are accused of driving under the influence. Refusing to give a sample can result in revocation of your driver's license and other penalties, which may cause you significant hardship. However, submitting to the test may also result in serious penalties. But if you submit to a test that shows that your blood-alcohol content is above the legal limit, are you hopeless in defending yourself?
Not necessarily. Particularly when blood and urine samples are taken, law enforcement personnel must adhere to strict procedures to ensure the chain of custody is not interrupted. In short, the chain of custody is the care and documentation of evidence from its initial collection to its presentation in court. Prosecutors must adequately establish the chain of custody in order to prove that the evidence has not be compromised. This leaves an opening for a defense to try to show that there are serious gaps in the chain of custody that may have compromised the validity of the evidence.
Pointing out these gaps can occur in many ways. For example, the prosecution may not have a witness to testify as to the initial collection process, or there may have been an error during the collection, storage or testing process. Likewise, a toxicologist may fail to adhere to his or her standard practices, which could draw the validity of the sample into question.
If you can successfully attack the chain of custody, then you may be able to have otherwise damaging evidence suppressed. Without this strong evidence to use against you, a prosecutor may have no other choice than to dismiss the drugged or drunk driving charges you face. Confronting DUI charges can be fraught with legalities like these, so it can be helpful to have an attorney on your side who knows how to utilize the system to your advantage.
Source: FindLaw, "How to Suppress Evidence," accessed on Aug. 28, 2016