The police can arrest someone when they have probable cause, which typically means an articulable suspicion that criminal activity has occurred. However, prosecutors will not be able to file charges if probable cause is all that officers can attest to. The state generally needs compelling evidence to pursue criminal charges. Witness testimony, physical evidence, security camera footage and business records are all among the types of evidence that can lead to a strong criminal case.
Prosecutors have to convince the courts beyond a reasonable doubt that a crime occurred. But even when the state seems to have evidence that clearly connects someone to a criminal incident, it is often possible for defendants to avoid a conviction. People can challenge the state’s evidence and potentially prevent it from having much of an impact on their case. These are the most common reasons for defendants and their lawyers to challenge evidence that prosecutors aspire to use in order to bolster their claims.
Illegal activity by the police
The Fourth Amendment and numerous court rulings have established, affirmed and expanded on the right of the general public to be free from unreasonable searches and property seizures. Police officers responding to a call or investigating a crime have to follow certain rules if they want to search an individual or their property. If police officers conduct a search without a warrant, probable cause or permission, it may be possible to ask the courts to exclude that evidence from the criminal proceedings due to the misconduct of the police officers.
Questions about the accuracy of the evidence
Perhaps the state used photo or video enhancement software to clear up an image that was blurry, or perhaps the prosecutor wants to use questionable forensic science, like blood spatter analysis or 911-call analysis to build its case. Issues with contamination, problems with record-keeping practices and objectively bad science are all reasons to challenge certain evidence during criminal proceedings. Bringing in an expert witness who can explain the issues with chemical contamination or image enhancement that might lead to inaccurate assumptions by those hearing the case could undermine the usefulness of certain evidence and raise doubts about someone’s involvement in criminal activity.
Challenging the evidence is one of multiple possible defense strategies that can work for those who have been accused of violating the law.