In order to convict you of any criminal offense, a prosecutor must prove all of the elements of that crime as set out in Pennsylvania criminal law. For example, if you are charged with possession of marijuana, the prosecutor would have to prove not only that you knowingly possessed and had control over the substance, but also that the substance in question was, in fact, marijuana. Appearance, smell, and other factors may not be enough to establish that a particular substance is marijuana or another type of illegal drug. Instead, prosecutors must present evidence to support the assertion that it was marijuana. This is one of many situations in which prosecutors will often make use of the services of a forensic laboratory.

A forensic lab is often part of a law enforcement agency and often helps engage in investigations to solve crimes. However, these labs also play an important role in the prosecution of many offenders when proving the elements of a crime requires scientific evidence. Labs employ technicians who are supposed to conduct tests on evidence according to specific scientific methods, which can render results that can either incriminate or exonerate individuals facing criminal charges. In Pennsylvania, much of this testing is done by the PA State Police Bureau of Forensic Services. Forensic evidence is often used in the following types of cases:

Drug crimes – testing substances to prove they are drugs

DUI – breath or blood tests to demonstrate blood alcohol content (BAC)

Sex offenses – to identify DNA evidence in semen or other tissue

Murder and other offenses – to identify DNA evidence that may have been left at the scene of the crime to identify or confirm the offender.

While much emphasis is often put on forensic testing in criminal trials, the people employed in these labs are only human and mistakes are often made. These mistakes are critical as a forensic lab error can result in a wrongful conviction and a person could end up being incarcerated for a crime they did not commit based on erroneous evidence. In fact, last year, the Federal Bureau of Investigation (FBI)–perhaps the most important law enforcement agency in the entire country–admitted that it had made crucial forensics errors in hundreds of cases over the past two decades, some of which resulted in offenders being wrongfully put to death or otherwise dying in prison. This only proves that forensics evidence is fallible and should be closely examined for errors in every criminal case.

Using Forensic Errors in Your Defense

Because forensic errors can so easily result in wrongful conviction and forensic evidence is often needed to prove allegations, a major defense strategy can be examining the actions of forensics lab technicians to identify any possible errors or signs that the test results may be unreliable. Some of the most common errors that may occur regarding evidence in forensic labs can include:

  • Allowing untrained technicians to handle samples
  • Mislabeling samples
  • Not properly storing samples
  • Waiting too long to test samples
  • Allowing the contamination of samples
  • Having samples that are missing for a period of time (breaking the chain of custody)
  • Not properly calibrating equipment
  • Not performing tests in accordance with scientific standards
  • Using contaminated equipment for testing
  • Failing to record test results in a timely or accurate manner
  • Falsifying test results
  • Failing to report test results that may exonerate a defendant

The above are only some of many different forensic errors that may occur in a lab. All of these have the potential to lead to wrongful conviction and imprisonment and so forensics should always be carefully examined by your defense attorney.

Call a Philadelphia Criminal Defense Lawyer Today to Protect Your Legal Rights

The way that forensic labs store and process evidence can have a significant impact on the outcome of your case. If you can establish that the chain of custody was broken or that there is a substantial probability that the evidence was mishandled, tainted, or that the lab results were unreliable for any other reason, it may justify keeping the evidence out of court. If a prosecutor is unable to present critical evidence, it can significantly weaken their case or even force them to drop entirely, potentially resulting in an acquittal or dismissal.

To determine whether a forensic error may be at issue in your case, call The Zeiger Firm today 215-546-0340 or send us an email through our online contact form.


Brian J. Zeiger, Esquire, is an experienced and successful criminal defense and civil rights attorney. He is a seasoned trial lawyer with significant experience before juries and judges. Brian understands civil rights cases, including Taser, Wrongful Death, Excessive Force, Police Brutality, Police Misconduct, Malicious Prosecution, Monell Claims, Sexual Assault, Prisoner’s Rights, Time Credit, Medical Malpractice, and Medical Indifference.