The Paradox of Consensus: Why 9 Agreeing Witnesses Might Be Dead Wrong

By: John Guidry

Sometimes, too much agreement makes me wonder. If you’ve seen as many witnesses testify as I have, you start to get suspicious when their stories miraculously line up so neatly. The Question: Do you believe them more because there are 9 witnesses versus 5? Or two witnesses versus one?

Most people (and jurors) think: “Wow, everyone agrees, so it must be true.” The Reality: Agreement isn’t always a good thing. In fact, perfect agreement is often a red flag that the system is broken.

The “Paradox of Unanimity” (Too Good to Be True)

Back in the day, under Jewish Law (the Sanhedrin), a capital crime required 23 judges.

• The Rule: If every judge found the defendant guilty, the suspect was deemed innocent and set free.
• The Logic: They understood that human beings rarely agree 100% on anything. If there wasn’t a single dissenting voice, it meant the defendant wasn’t adequately defended or the court was biased.

The Science Backs This Up Scientists call this the Paradox of Unanimity. According to a study by physicist Derek Abbott (cited in Phys.Org), as the group of unanimously agreeing witnesses increases, the chance of them being correct actually decreases until it is no better than a random guess.

• Why? Because in the real world, errors happen. Small variances happen. If 10 people pick the exact same suspect out of a lineup without hesitation, it is statistically more likely that the lineup was rigged (systemic error) than that 10 people had perfect memory.

The Phantom of Heilbronn: The Serial Killer Who Wasn’t

The best real-world example of this is the case of the Phantom of Heilbronn.

• The Evidence: Police found the same female DNA at 15 different crime scenes across France, Germany, and Austria.
• The Theory: They were hunting Europe’s most prolific female serial killer. The DNA evidence was consistent, overwhelming, and unanimous.

The Truth: The “Phantom” didn’t exist. It turned out to be a Systemic Error. The cotton swabs used to collect the DNA were accidentally contaminated by a woman working in the factory that made the swabs.

• Because the system was flawed (the swabs), the evidence was “perfectly” consistent. The unanimity was an illusion.

The Black Swan Problem

Scientists once thought that after seeing 142,832 white swans, they had proven that all swans are white. Then an explorer found a black one.

• The Lesson: Just because the prosecutor calls 20 witnesses to say the same thing doesn’t mean it’s true. It just means they are all looking at the same (possibly flawed) picture.
• My Job: I stand up and object: “Cumulative!” We don’t need to hear the same story 100 times. We need to hear the truth, which is usually messy, inconsistent, and human.

John’s 2026 Update: The Echo Chamber Effect

Note: In the past, witnesses agreed because of police pressure. In 2026, they agree because of the Internet.

1. Social Media Witness Contamination In 2026, before the police even arrive, witnesses have already gone on Nextdoor, Facebook, or Citizen to discuss what they saw.

• The Effect: They inadvertently align their stories. Witness A reads Witness B’s post, and suddenly Witness A “remembers” seeing the red shirt that Witness B mentioned.
• The Defense: We subpoena their social media history. If we can show the “unanimous” witnesses were chatting in a group thread before giving their official statements, we can prove their consensus is artificial.

2. AI & The “Perfect” Video The Paradox of Unanimity applies to digital evidence too.

• Deepfakes: If five different “videos” of an incident appear online, and they all look too perfect or identical in angle, we suspect AI generation or manipulation. Real life has bad lighting and shaky hands. Perfect stability and clarity are now markers of a fake.

3. “Rapid DNA” Bias Police now use portable “Rapid DNA” machines at the scene.

• The Risk: Just like the Phantom of Heilbronn, if the machine isn’t calibrated, or the cartridge is contaminated, it will give the same “Guilty” result 100 times in a row. We fight to check the calibration logs of the machine, not just the result slip.

Don’t Let the “Mob” Convict You

Just because everyone agrees that the Earth is flat doesn’t make it flat. And just because 10 witnesses say you did it doesn’t mean they aren’t all sharing the same wrong memory.

Call me at (407) 423-1117. Let’s find the Black Swan.

About John Guidry II

John Guidry II is a seasoned criminal defense attorney and founder of the Law Firm of John P. Guidry II, P.A., located in downtown Orlando next to the Orange County Courthouse, where he has practiced for over 30 years. With more than three decades of experience defending clients throughout Central Florida since 1993, Guidry has successfully defended thousands of cases in Orange, Seminole, Osceola, Brevard, Lake, and Volusia counties. He has built a reputation for his strategic approach to criminal defense, focusing on pretrial motions and case dismissals rather than jury trials.

Guidry earned both his Juris Doctorate and Master of Business Administration from St. Louis University in 1993. He is a member of the Florida Bar and the Florida Association of Criminal Defense Lawyers. His practice encompasses the full spectrum of Florida state criminal charges, with a particular emphasis on achieving favorable outcomes through thorough pretrial preparation and motion practice.

Beyond the courtroom, Guidry is a prolific legal educator who has authored over 400 articles on criminal defense topics. He shares his legal expertise through his popular YouTube channel, Instagram, and TikTok accounts, where he has built a substantial following of people eager to learn about the law. His educational content breaks down complex legal concepts into accessible information for the general public.

When not practicing law, Guidry enjoys tennis and pickleball, and loves to travel. Drawing from his background as a former recording studio owner and music video producer in the Orlando area, he brings a creative perspective to his legal practice and continues to apply his passion for video production to his educational content.