When the members of the Los Angeles Police Commission met behind closed doors last month to decide if a cop had been right to kill Dale Garrett, the two bullets in Garrett’s back raised serious concerns.

Det. Arthur Gamboa had insisted that Garrett left him no choice but to shoot when he pulled a knife and threatened to kill the detective during a botched drug bust. LAPD Chief Charlie Beck and the commission’s own watchdog agreed, recommending the oversight board find that Gamboa’s decision to open fire was within department rules.

But for a majority of the five-person commission, errors and inconsistencies in Gamboa’s account, along with the fact that he shot Garrett in the back, could not be ignored. In a divided vote, the commission concluded the detective was not believable. The shooting, the panel ruled, violated the LAPD’s policy on when officers are justified in using lethal force.

With that decision, the shooting became the latest in a series of incidents in which Beck and his civilian bosses disagree on whether an officer’s decision to use deadly force was appropriate. These cases have given rise to a rare vein of tension between the chief and commissioners, who otherwise have heaped praise on Beck since he took over the department 2 1/2 years ago.

Believing the officers in these cases were justified to open fire, Beck has either refused to impose any discipline on the officers or let them off with a simple reprimand in the earlier cases, The Times reported last month. That has left a majority of the commission increasingly concerned that Beck is undermining their authority and sending a dangerous message to the LAPD’s rank-and-file officers that the consequences for a unjustified shooting are minimal.

Beck must now decide how, if at all, to punish Gamboa and his partner for a deadly encounter that even the chief agrees was marred by mistakes.

It was shortly after noon on a cool, cloudless day in May when Gamboa and Det. Ronald Kitzmiller, members of a narcotics enforcement team, stepped out of the LAPD’s downtown headquarters and headed for their station about a mile away, according to an internal LAPD report. The copy of this report, and another one written by the commission, obtained by The Times, concealed the officers’ names. Gamboa was named in a different department document, and an attorney representing Garrett’s family named Kitzmiller.

Walking down Spring Street, they soon approached the bustling intersection at 5th Street, where trendy restaurants and stylish lofts put a pleasant gloss over the block’s alternate, less savory reality. For years, Spring and 5th — especially the southwest corner – has been a stamping ground for drug dealers, who skulk about and whisper offers of prescription pills, pot, and other drugs to passersby.

On a whim, the detectives decided to do some undercover work, according to the department report.

Kitzmiller pulled a $5 bill from his wallet, marked it with a pen and handed it to Gamboa. Dressed in street clothes that concealed his badge and handgun, Gamboa leaned against a wall on the corner as Kitzmiller watched from across the street, the commission summary said. Within a minute or two, Garrett, 51, approached, saying “Weed, Klonopin, weed, Klonopin,” Gamboa told investigators.

Gamboa asked for a Klonopin, a prescription drug that can give the sensation of intoxication, and told investigators that Garrett “quickly, forcefully grabbed — snatched the $5 from my hand, knocking it down in a rude manner.” As Garrett kept walking, Gamboa said he followed, demanding his pill.

What happened next is not clear.

In an interview shortly after the shooting, Gamboa told investigators that Garrett, while a few feet ahead, stopped and turned clockwise to face him while unfolding a large knife. “I am going to kill you,” the detective recalled Garrett saying. He insisted that he shot Garrett twice in the chest.

An autopsy, however, showed both bullets had struck Garrett on the left side of his back, making Gamboa’s account impossible. In February, Gamboa returned to the street corner with his commanding officer to go through the sequence of the shooting. This time, he said, Garrett had turned in the opposite direction.

A witness standing nearby told investigators that Garrett only turned at his waist, instead of spinning around completely. This, Beck said in his review of the shooting, could explain how Garrett was shot in the back. Or, Beck speculated, Garrett may have faced the detective and then continued to turn away, exposing the left side of his back. The chief, however, did not address how Garrett could have posed a deadly, immediate threat to the detective if either of these scenarios were accurate.

Another witness disputed this version altogether, saying Gamboa and Kitzmiller “sneaked up” behind Garrett and startled him, according to the commission’s report.

A knife was found under Garrett’s body, although the reports by the commission and chief do not clarify if it was found with the blade out or folded.

Beck and Commission President Richard Drooyan declined to comment on the case. The detectives did not respond to e-mails requesting comment.

The chief and commission agreed that the detectives’ decision to conduct a spur-of-the-moment drug operation was, in the commission’s words, “in clear conflict” with department rules and training guidelines. In particular, they found that Kitzmiller, who served as a supervisor in the detectives’ narcotics unit, should have known better.

For these actions, Beck could choose to discipline the men.

But the decision to shoot Garrett, Beck concluded, was reasonable. An officer in the same situation would have responded as Gamboa did, he said.

Drooyan and Commissioners Robert Saltzman and John Mack saw things differently. The evidence, the commissioners wrote in their report, “did not support an objectively reasonable belief that [Garrett] presented an imminent threat of death or seriously bodily injury” when Gamboa fired.

joel.rubin@latimes.com