Using graphic autopsy photos even he termed "horrific," a coroner told jurors Friday that a hockey dad killed in a fight with another father sustained injuries consistent with a violent and punishing attack.

On the first day of testimony in the manslaughter case of Thomas Junta, forensic pathologist Stanley Kessler dismissed suggestions that victim Michael Costin died from a minor assault or a hereditary condition.

"This is a substantial force injury," Kessler told the Cambridge, Mass., courtroom. "It takes a lot of trauma to tear ligaments and the ligaments at the back of his skull were torn."

Junta, a 44-year-old truck driver and father of two, faces 20 years in prison if convicted in the death of Costin, the informal referee of a scrimmage involving the sons of both men.

Prosecutors allege that the 275-pound Junta, who outweighed Costin by 100 pounds, pummelled him to death in a rage over rough play on the ice, but Junta claims he threw only three punches in self-defense after the other man sucker-punched him. His lawyers plan to call their own medical experts to bolster his account. The July 5, 2000, killing is considered the most extreme case of "sideline rage" — the phenomenon of parental violence in youth sports.

Minutes before the lunch recess on the first day of testimony, Kessler showed the panel of 10 women and four men bloody photos of the internal hemorrhaging and clotting Costin suffered.

Prosecutors plan to call bystanders to testify that Junta pinned Costin to the floor, punched him until both hands were sore and then slammed his head against the ground. Kessler, who performed the autopsy, said Costin's injuries were consistent with those accounts. The pathologist said Costin died after his neck was hyperextended and rotated — a wrenching that caused a major artery in his neck to tear.

Forensic pathologist Stanley Kessler

"One fourth of the supply of blood to the brain is over," said Kessler. "You can't survive."

During a combative cross-examination, Kessler admitted that bruises on the victim's knuckles might indicate he had thrown punches during the altercation. But, Kessler said, "He was just in a hockey game. I don't know how he got the bruises."

He also shrugged off a study, cited by defense lawyer Thomas Orlandi, that found fatal injuries like Costin's could be caused by minor assaults. Kessler said the study only concerned severely intoxicated victims and was "irrelevant" to the Junta case since alcohol dilates blood vessels.

Kessler and the prosecution fought to have jurors see the graphic photos over objections from Junta's defense. The pathologist said charts or diagrams would not properly convey the injuries, but Orlandi said the nature of the pictures might play on the jury's sympathies. Judge Charles Grabau allowed the photos, but ordered some cropped.

In front of jurors, Orlandi hammered away at the pathologist's decision to show the gruesome pictures, repeatedly suggesting he might have relied on diagrams. In a brief moment of levity, the doctor wrinkled his nose at defense diagrams, saying, "The colors are atrocious — orange, green and florescent yellow. I can't even look at this."

Earlier in the day, emergency workers gave jurors a detailed description of the disturbing scene at the Burbank Ice Arena in Reading following the fight. Sgt. James Cormier, the first police officer to arrive, said Junta was standing in front of the arena, his shirt torn and a cut on his face. Inside, Cormier testified, a crowd of children, some as young as 7, had gathered around Costin's splayed body.

"His color was ashen gray. His eyes were open and staring straight ahead, and he was motionless," said Cormier. The officer said he immediately yelled for the children to be moved away from the "traumatic" scene and began CPR on Costin.

Emergency medical technician David Gentile said he quickly examined Costin and noticed "his left ear and neck area was swollen and black and blue." Showing jurors a snapshot taken at the hospital of the unconscious victim with tubes in his mouth and blood on his face, the ambulance worker said Costin's nose was "crushed inward" and appeared to be broken.

Gentile said Costin was not breathing and had no pulse. Rescue workers used a defibrillator to jumpstart his heart, but those efforts proved unsuccessful.

"His pupils were fixed and dilated," said Gentile.

The trauma doctor who initially treated him testified briefly, saying Costin did not improve in the emergency room and rated only 3 on a scale where anything below 8 indicated severe brain injury.

Rink staffer Nancy Blanchard, expected to be a key prosecution witness, took the stand briefly Friday afternoon before court broke for the weekend. She said she called 911 after a woman told her two men were fighting in the rink. She said she found Costin and Junta scuffling with each other near the locker rooms while children looked on.

One small boy, she said, was crying and grabbing at the men. "That's my daddy," she recalled him saying.

Court is to resume Monday morning with the remainder of Blanchard's account. The trial is being broadcast on Court TV.