A judge declared a mistrial Monday in the hazing trial of five Florida A&M University fraternity members after the jury said it was perplexed by an undefined legal term and unable to reach a verdict.

The trial would have been the first to test a new state law that makes hazing a felony if it results in death or "serious bodily injury," but the law does not define the latter term.

Jurors deliberated for more than three hours, but the mistrial was declared about 20 minutes after they sent a note to Circuit Judge Kathleen Dekker asking for a more substantial definition of serious bodily injury. The jurors also asked how to distinguish between serious and moderate injury. She told the jury there was no further legal instruction.

"That is a very serious legal term and it has been defined in other statutes and yet for whatever reason it's not defined in this one," said defense lawyer Chuck Hobbs.

Dekker had instructed the six-member jury it means injury that is neither slight nor moderate.

Four Kappa Alpha Psi brothers were charged with using canes, boxing gloves and bare fists to beat aspiring fraternity member Marcus Jones, 20.

The Decatur, Ga.-native said he was beaten so severely over four nights of an initiation ritual that he suffered a broken ear drum and needed surgery on his buttocks.

The fifth defendant was accused of assisting in the alleged hazing by encouraging Jones and other would-be fraternity members to bear up under the beatings and revived them with water when they passed out from the pain.

The defendants accused of striking Jones are Michael Morton, 23, of Fort Lauderdale; Brian Bowman, 23, of Oakland, Calif.; Cory Gray, 22, of Montgomery, Ala., and Marcus Hughes, 21, of Fort Lauderdale. Jason Harris, 25, of Jacksonville, was accused of assisting them.

"This was no accident. This was no joke. This was not playtime at the frat house," Assistant State Attorney Frank Allman said in his closing argument. "This was intentional. This was dangerous."

Allman bypassed reporters by leaving the courtroom through a back door after the mistrial was declared. A telephone message left with the state attorney's office after hours was not immediately returned.

Florida's 2005 hazing law makes it a third degree felony, with penalties ranging from probation to five years in prison. The defendants were charged only with the felony so the jury could not convict them of a misdemeanor hazing charge.

The university has suspended the defendants pending the outcome of the criminal case. It also has suspended the fraternity until 2013 regardless of the outcome.