BARTOW, Fla. (AP) _ A man accused of dunking his 2-year-old stepson headfirst into a toilet goes on trial on murder charges this week in a case that raised questions about social workers' failure to protect the toddler.

Prosecutors will seek the death penalty for Thomas Coe, who told police he was punishing Bradley McGee for soiling his diaper. The boy's death brought unprecedented charges against four social workers, one of whom was convicted of child abuse.

''If nothing else, all this has made caseworkers be more careful to realize they're making life-or-death decisions here,'' said Pam Kirkland, the boy's foster mother before he was returned to Coe and the mother who abandoned him. ''With every child, they have to stop and ask - 'Could this be the next Bradley McGee?'''

Coe, 23, goes on trial Tuesday in Fort Myers. Defense attorneys have acknowledged the dunking but say Coe did not intend to kill the boy, so it wasn't murder.

''We just want to make sure that if he's convicted, he gets convicted for the crime he committed,'' said attorney Robert Norgard.

The case grew beyond domestic violence as Bradley's road from abandonment to foster care and ultimately back into the hands of his troubled parents made him a symbol of failings in the state's social services system.

The boy was under the supervision of the state Department of Health and Rehabilitative Services from the time he was 4 months old, after his mother abandoned him at a shopping mall with a pretzel vendor.

He died of head injuries July 28, 1989, two months after a judge followed an HRS recommendation and ordered the child returned to his stepfather and mother, Sheryl McGee Coe.

The death prompted the Legislature last fall to allocate $39 million for more child protection workers. Legislators also changed the law to make child safety, not family reunification, the social services agency's top priority.

According to Coe's statements to investigators, the dunking came during potty training when Bradley dirtied his diaper.

After Mrs. Coe took Bradley out in the yard and hosed him down, Coe took him into the bathroom, grabbed the boy by the ankles and dunked him in the toilet bowl.

''Plunger style,'' a detective wrote.

When Bradley refused to stop screaming, he was put under a cold shower, then led down the hall to the living room.

Coe said he and his wife then hit the staggering Bradley in the head with pillows until he suddenly stiffened, collapsed and curled into a fetal position. Efforts to revive him failed.

Both parents were charged with first-degree murder and aggravated child abuse. Mrs. Coe, 21, pleaded no contest earlier this year to second-degree murder and is serving a 30-year prison term.

Coe is described by relatives as a brooding, angry young man in constant pain from a congenitally crippled hip and hereditary kidney disease.

In statements to prosecutors, Mrs. Coe said the toilet-dunking was the culmination of a pattern of abuse by her husband against Bradley. She claims he urinated on the child, put cayenne pepper on his genitals and dunked him in the toilet at least once before.

Defense attorneys argue Coe dunked the child to discipline him, not to harm him.

Within weeks of Bradley's death, charges were filed against four state social workers. Three were cleared before Bradley's main caseworker, Margaret Barber, 62, was convicted last month of child abuse and placed on three months' probation.

Ms. Barber had recommended that the boy be returned to his parents without showing the court a psychological report that described the Coes as explosive, infantile and unable to care for children.

''I still lay awake at night and wonder how it could have happened - how it all could possibly have been prevented,'' said Ms. Kirkland, who cared for Bradley for 14 months. ''There's no way I can put it out of my mind.''