Two small details made a big difference in the trial of retired NBA star Jayson Williams (search), who was acquitted of the most serious charge he faced in the shooting death of a hired driver at his New Jersey mansion.

One detail was the shotgun's firing mechanism, which the defense said contributed to a fatal misfire. The other was a critical instruction from the judge that allowed the jury to consider whether Williams was merely negligent, as opposed to reckless.

Both points played a role in acquitting Williams of aggravated manslaughter, and leaving the jury deadlocked on a charge of reckless manslaughter, according to interviews with jurors.

However, the jury did convict Williams of four charges, including witness and evidence tampering. Together, the four charges carry up to 13 years in prison.

The split verdict means that Williams faces the possibility of a retrial, as well as prison time for attempting to conceal the shooting of chauffeur Costas Christofi (search).

Testimony revealed that Williams' 1993 Browning Citori double-barreled 12-gauge shotgun had a firing mechanism that was worn, and fouled with rust, oil and tiny wood chips.

Several jurors agreed with a defense weapons expert, Richard N. Ernest, that the shotgun malfunctioned when Williams snapped it shut while holding it in one hand, causing it to fire.

"There is a great probability that it did," juror Ann Stengel said.

Jurors also said they carefully evaluated the judge's legal instructions on the elements of aggravated manslaughter and reckless manslaughter. For both, a conclusion of negligence requires a verdict of not guilty.

"It wasn't reckless. It was negligence," juror Tonja Poto said. She and Stengel said they were among eight jurors who voted not guilty on the reckless manslaughter charge. Four voted guilty, leading to the deadlock.

The prosecution had fought to delete the negligence instruction, arguing that the term had not arisen during the trial. "It will be confusing to the jury to inject 'negligence,' " First Assistant Hunterdon County Prosecutor Steven C. Lember told the judge before deliberations.

Judge Edward M. Coleman (search), however, sided with the defense, which maintained that court rulings gave precedence for including the instruction.

So the jury was told that for it to convict on either manslaughter charge, it had to conclude Williams was reckless because he disregarded the risk of causing death.

The instructions defined negligence as a "failure to perceive" the risk that death could result from his conduct.

In addition to recklessness, aggravated manslaughter required a finding that Williams acted under "extreme indifference to human life."

The shooting took place as Williams was giving friends and members of the Harlem Globetrotters a tour of his estate in western New Jersey in the early hours of Feb. 14, 2002.

Testimony showed Williams took a loaded shotgun from a cabinet, cracked it open, turned, uttered an obscenity at Christofi and snapped it closed. It then fired once, sending 12 pellets into Christofi's chest. He died within minutes.

Five witnesses testified Williams then wiped down the shotgun, and four said Williams placed it in the victim's hands.

Besides claiming it was an accident, the defense asserted that the former NBA All-Star was so distraught after the shooting he could not organize a cover-up.

The Hunterdon County prosecutor's office must choose whether to pursue a retrial on the charge of reckless manslaughter, which carries up to 10 years in prison. The office has until May 21, when a scheduling conference is set.

A decision in favor of a retrial could produce plea negotiations, legal experts said. A plea deal probably would require Williams to accept some prison time, said James Cohen, professor of criminal law at Fordham Law School.

Williams, 36, retired from the New Jersey Nets in 2000.