An Army drill sergeant was found guilty of involuntary manslaughter and dereliction of duty today in the heatstroke death of a Fort Jackson recruit last summer.

Sgt. Willie Alexander was sentenced to six months confinement at hard labor, loss of two-thirds of his $668 monthly pay for six months, and reduction to the lowest enlisted grade.

A seven-man military jury deliberated one hour and 40 minutes before convicting Alexander, 24, a six-year veteran, in the June 29 death of Wayne Krassow, 18, of Cygnet, Ohio.

"I know within my heart and within my mind that I'm innocent," he said after the verdict.

Alexander was acquitted of involuntary manslaughter in that day's death of a second recruit, Lester Watts, 18, of York, S.C., and also was acquitted of maltreatment of both recruits.

Krassow and Watts died after strenuous exercises the day they arrived at their company area to begin 6 1/2 weeks basic training. Post officials had banned all physical training that day because of high humidity and 105-degree heat. The post is the Army's largest recruit training base, with a daily average of 7,477 male and female recruits.

A second drill sergeant, Sgt. 1st Class Lawrence Chapman Jr., was convicted Dec. 4 of dereliction of duty and one negligent homicide. He was acquitted of all charges in Watts' death, was fined $500 and demoted one rank to staff sergeant.

If convicted of all original charges, each sergeant could have faced up to six years and three months confinement at hard labor, dishonorable and forfeiture of all pay and allowances.

The case had attracted national attention, embarrassing Army officials who had insisted excessive discipline and maltreatment were things of the past. The deaths resulted in significant changes in training practices, including restrictions on physical exercises for arriving recruits.

Though some testimony conflicted, withnesses said Alexander refused requests for water, kicked one recruit and challenged others to fight, and screamed and cursed at them throughout the day. Witnesses said Krassow collapsed about five times and Watts collapsed twice.

Several recruits said Alexander inserted open ammonia capsules into Krassow's nostrils when the recruit collapsed the last time. They said he shouted, "This one's dead; get a shovel and bury him," ordered trainees to drag the unconscious man down the company street where he was later found unattended.

One witness testified Alexander kicked a recruit in the back, called him a "freak" and tossed a dime on his chest, saying, "Call me when he dies." The recruit was not identified.

Alexander testifed that the "bury him" shout at Krassow was intended to "scare him so he would get up." He said he ordered Krassow dragged away so that he wouldn't have to "breathe heavy dust" in the exercise area.

Alexander said he ordered repeated sets of pushups for recruits, and ordered one man to carry a log all day for calling him "sir" instead of "drill sergeant." But Alexander denied singling out the dead recruits for special punishment other than knocking Krassow to his knees by "tossing" him a 25-pound sandbag.

Defense lawyers contended that Alexander was not told of the eericse ban and that recruits confused him with another drill sergeant.

In an emotional closing argument today, the chief defense attorney, Capt. Kenneth Allen, told the jury Alexander was being "railroaded" by the Army for following routine training practices. "He performed a duty that was given to him." Allen said.