PANAMA CITY, Fla. — Seven former boot camp guards and a nurse were acquitted today of manslaughter in the death of a 14-year-old boy who was hit and kicked by the drill instructors in a videotaped altercation.

The all-white jury took about 90 minutes to decide whether the guards were responsible for the death of a black teenager, Martin Lee Anderson. The guards, who are white, black, and Asian, stood quietly as the judge read the verdicts.

Surveillance video shows the guards striking the limp boy with their fists and knees in January 2006. The case caused protests in the state capital and prompted Florida to close its juvenile boot camp system.

The guards also dragged Anderson around the military-style camp’s exercise yard and forced him to inhale ammonia capsules in what they said was an attempt to revive him. The nurse stood by watching.

Defense attorneys argued that the guards properly handled what they thought was a juvenile offender faking illness to avoid exercising on his first day in the camp. They said Anderson’s death was unavoidable because he had undiagnosed sickle cell trait, a usually harmless blood disorder. The disorder can hinder blood cells’ ability to carry oxygen during physical stress.

The defendants would have faced up to 30 years in prison had they been convicted of aggravated manslaughter of child. The jury could have convicted them of lesser charges, including child neglect and culpable negligence, but did not.

Prosecutors said the eight defendants neglected the boy by neglecting his medical needs after he collapsed while running laps. They said the defendants suffocated Anderson by covering his mouth and forcing him to inhale ammonia.

“You may not hear anything coming out of that video sound-wise, but that video is screaming to you in a loud, clear voice, it is telling you that these defendants killed Martin Lee Anderson,” prosecutor Scott Harmon said in his closing argument.

Anderson died January 6, 2006, when he was taken off life support, a day after the altercation. The case quickly grew and shook up the state’s boot camp and law enforcement system amid the boy’s family alleging a cover-up.

An initial autopsy by the medical examiner for Bay County found Anderson died of natural causes from sickle cell trait. A second autopsy was ordered and another doctor concluded that the guards suffocated Anderson through their repeated use of ammonia capsules and by covering his mouth.