Piazza v. Mayne

What This Case Is About

Piazza v. Mayne addresses malicious prosecution claims under § 1983 and the role of qualified immunity when an officer initiates a prosecution based on arguable probable cause. The Fifth Circuit affirmed summary judgment for the defendant officer, holding that his investigation and decision to pursue charges were objectively reasonable.

The Facts

On July 27, 1993, Jeff Mayne, an enforcement agent with the Louisiana Department of Wildlife and Fisheries, inspected a truck containing a 1,121-pound shipment of hybrid striped bass belonging to Paul Piazza, a licensed wholesale seafood distributor. Mayne contacted the Department and discovered that Piazza had reported a purchase of 2,543 pounds of hybrid striped bass from a Texas company on July 21, 1993 — six days earlier.

Mayne believed the fish looked “too fresh” to be from the six-day-old purchase. He seized the shipment and took a sample to Department biologists John Burdon and Howard Ragillio. They examined the fish and opined that they had been harvested less than 72 hours before the inspection. Based on this, Mayne suspected that Piazza was illegally selling fish that were not properly documented — a violation of Louisiana wildlife regulations.

Mayne pursued charges against Piazza. The prosecution was ultimately unsuccessful — the charges were dismissed. Piazza then sued Mayne under § 1983 for malicious prosecution in violation of the Fourteenth Amendment.

What the Court Decided

The Fifth Circuit affirmed summary judgment in Mayne’s favor on qualified immunity grounds.

The court applied the elements of a § 1983 malicious prosecution claim: (1) the commencement or continuance of criminal proceedings against the plaintiff, (2) the absence of probable cause, (3) malice, and (4) favorable termination. The key issue was whether Mayne had probable cause — or at least arguable probable cause — to pursue the prosecution.

The court found that Mayne’s investigation provided an objectively reasonable basis for the charges. He observed fish that appeared fresher than their purported age, consulted with qualified biologists who confirmed his suspicion, and followed standard investigative procedures. Even if his conclusions were ultimately wrong, his actions fell within the range of reasonable professional judgment.

The court emphasized that qualified immunity protects officers who make reasonable mistakes. Mayne was not required to be correct — he was required to be reasonable. His reliance on expert opinions and physical evidence, combined with the documentation discrepancies, gave him at least arguable probable cause.

Why This Case Matters for Your § 1983 Case

• Malicious prosecution requires proving no probable cause: The most difficult element of a malicious prosecution claim is showing that the officer lacked probable cause to initiate proceedings. If the officer can point to any reasonable basis for the charges, qualified immunity will likely apply.
• Arguable probable cause is enough for immunity: Officers don’t need actual probable cause — they need only arguable probable cause, meaning a reasonable officer could have believed the evidence supported the charges.
• Expert opinions bolster probable cause: When an officer consults with experts (biologists, forensic analysts, medical examiners) who support the officer’s suspicions, this reliance on expert judgment strengthens the probable cause argument.
• Favorable termination is necessary but not sufficient: Even though the charges against Piazza were dismissed — satisfying the favorable termination requirement — the absence of probable cause still had to be proven independently.
• The investigation’s quality matters: If the officer conducted a genuine investigation, consulted relevant experts, and followed procedures, courts are reluctant to second-guess the decision to prosecute — even when the prosecution fails.

Key Takeaway

To defeat qualified immunity on a malicious prosecution claim, you must show not just that the charges were ultimately dropped, but that no reasonable officer could have believed probable cause existed when the prosecution was initiated. Officers who investigate, consult experts, and act on reasonable — even if mistaken — conclusions are protected by qualified immunity.