Relying heavily on a grainy, amateur video recording that provoked nationwide alarm, the San Bernardino County district attorney charged a sheriff's deputy Tuesday with attempted voluntary manslaughter for opening fire on an unarmed Air Force policeman after a high-speed pursuit.

Deputy Ivory John Webb Jr., charged in the Jan. 29 shooting of Airman Elio Carrion, becomes the first law enforcement officer ever charged in an on-duty shooting in San Bernardino County.

"Deputy Webb shot Mr. Carrion and intended to kill him," said Dist. Atty. Michael A. Ramos. "This is a very difficult decision for us. But when the facts say a crime has been committed, it is our duty to file charges. We will let the community decide if it's a crime."

If convicted, Webb will face up to 18 1/2 years in state prison, though he could have faced more had Ramos charged him with attempted murder.

Legal experts agree that obtaining a conviction is far from certain, however, pointing out that Southern California juries have traditionally been reluctant to find police officers guilty of misconduct, even when their alleged crimes are taped.

For example, when four LAPD officers were charged in state court for their roles in the videotaped beating of Rodney King in 1991, a jury in Simi Valley acquitted them. Two of the officers were later convicted of civil rights violations in federal court.

"The problem with videotape is the action often starts before the tape is rolling and goes on after it stops," said Loyola Law School professor Laurie Levenson, a former federal prosecutor. "There are things going on that aren't always reflected, such as what people outside the frame are doing, what the defendant may be doing but can't be seen, or what is being said."

In the San Bernardino County case, the shooting occurred after Webb was involved in a brief high-speed pursuit of a Corvette on the night of Jan. 29. Carrion was a passenger in the car, which crashed into a fence.

In a digital video recording of the incident captured by a neighborhood resident, Webb appears to order Carrion to "get up" from a sprawled position on the pavement. When Carrion starts to rise, Webb shoots him three times.

Ramos said the deputy's intentions seemed clear: "[Webb's] belief there was a danger was unreasonable. That's why it's attempted voluntary manslaughter."

The attorney for Carrion's family said he was "extremely disappointed" by the district attorney's decision not to charge Webb with attempted murder. "When Webb moved his body to get a better angle, so he could shoot at Elio's upper body -- his heart -- that's attempted murder," Luis Carrillo said. "This decision shows a lack of justice."

Carrion, 21, was shot in the chest, shoulder and leg, and he continues to recover at an undisclosed medical facility in Southern California. Carrion had just returned from Iraq when he was shot, and he was due to report back to his unit, the 2nd Security Forces Squadron, at Barksdale Air Force Base in Shreveport, La. He could not be reached for comment.

Ramos said that to convict Webb of attempted murder, prosecutors would have to prove the deputy acted with malice -- that he intended to kill Carrion without justification. Ramos said he concluded that Webb may have felt he was in danger, but that the deputy's belief was "unreasonable."

Webb is scheduled to surrender and be arraigned today in San Bernardino County Superior Court on a count of attempted voluntary manslaughter, with special allegations of inflicting great bodily injury and using a firearm.

To convict Webb of attempted voluntary manslaughter, prosecutors must prove the deputy tried to kill Carrion in a sudden quarrel or heat of passion, and that he acted unlawfully but not with malice.

The deputy, an eight-year Sheriff's Department veteran, is the son of a former Compton police chief. Webb also was a University of Iowa wide receiver who played for the Hawkeyes in the 1982 Rose Bowl.

Neither Webb nor his father returned phone messages left at their homes. Webb's attorney, Michael Schwartz, did not return calls to his office.

Previously, Webb's father told The Times that his son had felt threatened when Carrion started to stand up, and that he had only a "split second to react." The elder Webb also questioned the quality of the video recording, saying his son may have told Carrion "Don't get up" before opening fire.

Ramos' office has never prosecuted a law enforcement officer involved in an on-duty shooting or in-custody death. Since 2000, the district attorney has reviewed 131 officer-involved shootings and in-custody deaths in the county.