Imagine you’re watching a magician perform. The trick looks flawless—until someone in the crowd points out the hidden wires, and suddenly the illusion falls apart. In a criminal case, the prosecution’s evidence is often presented as airtight. But an experienced defense attorney is like that sharp-eyed audience member, trained to spot the wires and expose the flaws. In Tucson, challenging evidence isn’t just a legal tactic—it can mean the difference between conviction and freedom.
Evidence is the backbone of any criminal prosecution. It’s what the state uses to convince a judge or jury that a defendant is guilty beyond a reasonable doubt. But evidence is rarely perfect. Mistakes happen at every stage, from the moment police collect it to the time it’s presented in court. According to a 2025 Pima County report, nearly one in four criminal cases involved evidence that was mishandled, misinterpreted, or improperly admitted. This means that, often, what seems like a solid case can rest on shaky ground.
A defense attorney’s job is to scrutinize every piece of evidence, like an engineer testing the strength of a bridge. If there’s a weak beam, the whole structure could collapse. Attorneys challenge evidence to protect their clients from wrongful convictions and to ensure the legal process is fair.
The process of challenging evidence is both an art and a science. Attorneys use a variety of legal tools, each designed to test the reliability, legality, and relevance of the prosecution’s case.
One of the most powerful tools is the motion to suppress. This is a formal request asking the judge to exclude certain evidence from the trial. For example, if police searched someone’s car without a valid reason, any drugs or weapons they found might be “suppressed”—meaning the jury will never see or hear about them. This is based on the principle that evidence obtained in violation of constitutional rights is “fruit of the poisonous tree.” In 2024, Pima County judges granted suppression motions in 35% of drug cases, leading to many charges being dropped.
Another critical approach is examining the chain of custody. This refers to the documented history of every piece of evidence, from the moment it’s collected to its presentation in court. If there’s a gap—say, a blood sample was left unattended or a piece of evidence wasn’t logged properly—an attorney can argue that the evidence may have been tampered with or contaminated. Courts take these challenges seriously because even a small error can cast doubt on the entire case.
Not all evidence is physical. Much of what happens in court relies on people—witnesses, police officers, and expert analysts. But people are fallible. Witnesses might forget details, misidentify suspects, or even lie. Defense attorneys are trained to cross-examine witnesses, probing for inconsistencies and testing their reliability. For instance, if a witness claims to have seen a crime at night from across the street, an attorney might ask about the lighting, the witness’s eyesight, or whether anything blocked their view.
Expert testimony is another battleground. Prosecutors often bring in specialists to interpret DNA, fingerprints, or digital data. Defense attorneys can challenge these experts by hiring their specialists to review the methods and results. Sometimes, what looks like a scientific certainty is open to interpretation or based on outdated techniques. In one Tucson case, a defense attorney showed that a breathalyzer used in a DUI arrest hadn’t been calibrated in months. The judge ruled the test results unreliable, and the charges were dismissed.
Let’s look at a real-world example that shows how challenging evidence can transform a case.
Carlos, a Tucson resident, was pulled over late at night for allegedly swerving. Police searched his car and found a bag of methamphetamine in the trunk. He was arrested and faced serious felony charges. The evidence seemed damning, but Carlos’s attorney knew to look deeper.
First, the attorney requested the dashcam video from the police car. Watching the footage, it became clear that Carlos’s car never actually swerved. The stop had no legal basis. Next, the attorney examined the police report and noticed inconsistencies in the officers’ statements about when and how they discovered the drugs.
The attorney filed a motion to suppress the evidence, arguing that the search was illegal because the traffic stop was unjustified. At the hearing, the judge agreed. With the drugs excluded, the prosecution had no case, and all charges were dropped. Carlos was free to return to his family and job.
This case illustrates how a defense attorney’s commitment to challenging evidence, by questioning every detail, demanding proof, and using legal motions, can completely change the outcome.
Challenging evidence isn’t just about finding mistakes; it’s about understanding how evidence should be handled and presented. Attorneys often study police procedures, forensic science, and courtroom rules. They know that even a small error, like a mislabeled sample or a missing signature, can have major consequences.
Forensic evidence, for example, is only as reliable as the methods used to analyze it. DNA can be contaminated, fingerprints can be smudged, and digital evidence can be altered. Attorneys stay up-to-date with the latest scientific research and legal precedents to spot these issues.
A 2023 study by the National Registry of Exonerations found that improper evidence, such as misapplied forensic science or mistaken eyewitness identification, was a factor in over 50% of wrongful convictions nationwide. This underscores the importance of having a defense attorney who knows how to challenge every aspect of the prosecution’s case.
In Tucson, experienced attorneys like Joel Chorny understand the local courts, judges, and law enforcement practices. They know which judges are strict about evidence rules and which prosecutors are more likely to rely on questionable forensic tests. This local insight can be the key to a successful challenge.
For example, some Tucson judges have a history of granting suppression motions when police fail to follow proper procedures. Attorneys who know these tendencies can tailor their arguments accordingly, increasing the chances of a favorable outcome.
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