The Marine Corps is charging a company commander with negligent homicide for pushing his troops on a fast march through a hot North Carolina night, leading to the death of a 21-year-old reservist who began vomiting just three miles into the eight-mile hike, officials said yesterday.

It is rare for the military to take criminal action against an officer in connection with a training death; Marine officials could recall only a handful of cases over the past few decades. An investigative report on the last hours of Lance Cpl. Giuseppe Leto describes what was supposed to be a routine conditioning march but turned into a hellish experience for a company of Marines at Camp Lejeune, N.C.

Leto was a reservist on summer break from a student's life taking business courses at Western New England College in Springfield, Mass. He died after completing the eight-mile hike in 80- to 85-degree temperatures on July 7.

According to investigators, he showed signs of heat-related stress -- vomiting, dry heaving, excessive sweating -- at the first rest stop, less than halfway into the hike. By the second rest stop, he was pale, breathing heavily and appeared exhausted.

During the final leg, Leto refused a suggestion that he board a truck carrying Marines who were unable to finish. At the end of the march, he wandered about seven-tenths of a mile away and collapsed. He was found unconscious nearly two hours later, and investigators ruled that the cause of death was "heat illness."

Capt. Victor A. Arana, commander of the ill-fated Company B at Camp Lejeune's School of Infantry, faces charges not only of negligent homicide but also dereliction of duty and failure to obey a lawful order. His civilian attorney, Mark Stevens, said last night that Arana would plead not guilty at a preliminary hearing next month to determine whether to convene a court-martial. If convicted, he could be dishonorably discharged from the military and sentenced to more than 3 1/2 years in prison.

The nighttime hike was part of advanced training in weapons and combat techniques that Marines undergo after finishing boot camp. Leto had been excited about the session, which brought together reservists from across the country.

"He said he felt fine and was having a great time," recalled Annamaria DesBiens, Leto's cousin, who spoke with him by phone a few days before his death.

Stocky and athletic, Leto was an avid wrestler and lacrosse player. "He was just one big muscle," DesBiens said.

Marine investigators allege that Arana marched his men faster than specified in training guidelines. The rule book calls for a rate of 2.5 miles per hour for 45 minutes, followed by a 15-minute break. Company B covered three miles in the first hour, finally pausing for what some witnesses reported was a less than 10-minute rest. The second rest stop, before the final leg of the march, was said to have been even shorter.

Arana also is accused of failing to ensure that there were enough supervisors during the march and for not instituting a buddy system among the Marines. Additionally, he was cited for leaving his unit too quickly at the end of the hike.

Another Marine, Staff Sgt. Eric Baker, was faulted by investigators for not promptly taking a head count at the completion of the hike, which probably would have revealed that Leto was missing. But a Camp Lejeune spokesman said yesterday that no disciplinary action has been taken against Baker.

One month after Leto's death, a Marine sergeant assigned to a mortar unit collapsed during a field exercise at Camp Lejeune and died. A base spokesman said yesterday that death resulted from a heart attack, and no one is likely to be charged in connection with it.

Marine spokesmen were unable to provide statistics yesterday on other training fatalities in recent years, but they said most such cases have not led to criminal prosecutions.

"It's unusual because the commanders we have tend to be pretty responsible, and there are a lot of systems -- checks and balances -- built into this training to prevent accidents from happening," said a senior Marine attorney.

In perhaps the most famous instance of Marine training misconduct, a drill instructor was court-martialed in 1956 after six recruits drowned during a night hike at the boot camp at Parris Island, S.C.

In the mid-1970s, another drill instructor at Parris Island was brought up on charges after a Marine died in a training fight with pugil sticks. And in 1989, a Marine lieutenant was convicted of dereliction of duty for the death of an enlisted man who was left behind during a training exercise in California's Mojave Desert. He was dismissed from the Marines and sentenced to four months in prison. Two sergeants were convicted of negligence and reduced in rank.