How Do Federal Defense Lawyers Challenge Forensic Evidence?

Forensic evidence plays a crucial role in many criminal trials, often being the deciding factor between conviction and acquittal. As a defendant, having an experienced federal defense lawyer who knows how to effectively challenge questionable forensic evidence can mean the difference between freedom and years behind bars. Here are some of the main ways federal defense attorneys dispute forensic evidence in court:

Scrutinizing the Collection, Handling, and Storage of Evidence

One of the most common ways forensic evidence gets called into question is improper collection, handling, and storage by police and investigators. Even minor gaps in the chain of custody or contamination of evidence can undermine its credibility in court. Defense lawyers thoroughly review all records related to evidence collection and handling to identify any discrepancies, mistakes, or violations of protocol.

Some examples of collection and handling issues that could lead to evidence being ruled inadmissible include:

• Lack of proper documentation showing chain of custody
• Failure to follow established protocols for evidence collection
• Improper storage conditions leading to degradation or contamination
• Evidence mishandling or tampering

If there are legitimate concerns about how evidence was gathered and maintained, a defense attorney can file a motion to suppress that evidence from being used at trial.

Questioning Relevance and Probative Value

Not all forensic evidence brought by the prosecution is equally relevant or probative to the case at hand. Skilled defense lawyers challenge forensic evidence by arguing it has little or no bearing on the charges against their client.

Examples include:

• DNA evidence that only shows the defendant was present at some point, rather than proving they committed a crime
• Partial fingerprint or shoe impressions that could match thousands of other people, not just the defendant
• Gunshot residue that only indicates proximity to a fired gun, not who fired it
• Evidence that establishes some association, but does not directly implicate the defendant in criminal acts

When forensic evidence has low probative value, defense attorneys work to minimize the weight and consideration it’s given compared to other more relevant evidence.

Seeking Exclusion Based on Constitutional Violations

If evidence was obtained illegally through violations of a defendant’s constitutional rights, defense lawyers can petition the court to suppress that evidence under exclusionary rule precedents.

Some examples include:

• Evidence from warrantless searches that violate 4th Amendment protections against unreasonable search and seizure.
• Incriminating statements obtained through coercive interrogations violating 5th Amendment rights.
• Evidence derived from other constitutional violations, like excessive detentions (4th Amendment) or compelled testimony (5th Amendment).

When investigators violate constitutional boundaries to obtain evidence, exclusion is the primary remedy available to defendants.

Advancing Alternate Theories

Often the most effective approach is not to attack the forensic evidence itself, but to advance plausible alternate theories that are consistent with the evidence.

Defense lawyers work creatively to identify and highlight scenarios other than the prosecution’s claims that reasonably fit the facts and forensic evidence. For example:

• Fingerprints or DNA at a crime scene that could have innocently gotten there well before the crime occurred.
• Injuries sustained by an alternate cause than the prosecution alleges.
• Digital evidence that was fabricated or planted on a defendant’s device.
• DNA evidence from a consensual encounter, not a sexual assault.

Advancing common sense alternate theories can create enough reasonable doubt in jurors’ minds to overcome otherwise convincing forensic evidence.

Emphasizing Lack of Additional Evidence

Skilled defense lawyers emphasize not just flaws in the forensic evidence presented, but any lack of corroborating evidence you would expect to see if the prosecution’s allegations were true.

For example:

• No eyewitnesses placing the defendant at the crime scene.
• No physical evidence indicating the defendant’s possession or use of a weapon.
• No DNA evidence implicating the defendant found at the crime scene.
• No records of the type of materials needed to construct an explosive device alleged.

Pointing out gaps in the evidentiary record along with flaws in whatever limited forensic evidence the prosecution presents can undermine the overall strength of their case.

Conclusion

While forensic evidence can appear daunting for criminal defendants, federal defense lawyers have ample strategies to call into question unreliable or inconclusive forensic proof. Thorough investigation, astute scientific critique, and advancing alternate theories provide ways even seemingly solid forensic evidence can be overcome. With an experienced federal defense attorney challenging the forensic evidence against you in court, there is hope for achieving justice even in the face of questionable science.