• Three departments — Orland, Dixon and Suisun City — said they lost records of their policy findings regarding a shooting.

• Avenal police in Kings County created internal review documents 11 days after receiving the news agencies’ request for the missing records related to two 2017 deadly shootings. The police chief declined to explain his department’s internal investigation protocols. Both incidents were found to be “in policy.”

• One hundred and five departments did some kind of review, but many showed no documented analysis or recommendations. For example, Yreka police in Siskiyou County “did not follow the standard (internal affairs) procedure” when officers fatally shot a man because “no citizens complaint was ever filed” and no allegations of wrongdoing were brought, a captain wrote to the department’s chief. “No questions were ever asked by the Yreka Police Department.”

A spokeswoman for California’s Commission on Peace Officer Standards and Training wrote in an email that police departments aren’t required by law to look at deadly incidents, but they’d “be exposed to tremendous liability” by failing to do so.

Regardless of the lack of a mandate, police trainer Gary Gregson, who spent seven of his 30 years as a Sacramento officer working in internal affairs, said every agency should examine what cops might have done wrong.

“The whole process is not only about managing risk and liability; it's an opportunity for the organization to make itself better," he said.

For example, if Pittsburg police had investigated Martinez's death, they might have raised questions about whether Mejia understood the hold he tried to use.

“I put him in a chokehold," Mejia said to his supervising sergeant as medical personnel tried to revive Martinez, body-camera video shows.

But Sgt. James Terry was quick to suggest a different term: “In the carotid.”

“In the carotid,” Mejia repeated.

Those terms have very different meanings, said Jim Boydd, a former police officer who now trains cops on how to safely use what's often called a “carotid hold” or “sleeper hold,” although Boydd’s preferred term is a “vascular neck restraint.” In that hold, an officer applies pressure to arteries on the sides of the neck, restricting blood flow to the brain, causing the person to pass out. It is not considered deadly force because it’s intended only to restrain a suspect, not kill them.

Boydd wouldn't comment on specific cases but said if done correctly, the carotid hold doesn't block the airway. “The person has to maintain the ability to breathe, obviously,” he said.

A chokehold does the opposite, applying direct pressure to the front of the throat, Boydd said, and cutting off breathing. That hold can be deadly and isn’t supposed to be used unless an officer’s life is in immediate danger.

The doctor who performed Martinez's autopsy testified in court that the man's airway was obstructed for four to six minutes.

Michael Haddad, a lawyer for Martinez’s family, said in an interview he suspects Pittsburg didn’t investigate because police feared a finding that Mejia broke use-of-force rules could be used in a lawsuit. He said the department's failure to properly train officers in the risky technique amounts to deliberate indifference. And, he said, the department can't correct mistakes if it doesn't look for them.

“They seem to be making no effort to try to prevent something similar from happening to someone else,” Haddad said.

Pittsburg’s attorneys argued in court documents that Mejia properly applied the carotid hold and pointed to Martinez’s drug use and weight as contributing factors in his death.

Martinez’s death wasn’t the only one attributed to suffocation by a cop, news organizations found.

In 2016, Wendell Celestine, 37, died during a violent struggle with Antioch police officers Mark Moraga and Michael Mortimer. The officers were trying to arrest Celestine, who had a history of grand theft, robbery and drug crimes dating to 1996, for a parole violation.

Records of the incident released under SB 1421 state that Mortimer hit Celestine repeatedly with a flashlight. Moraga used a carotid hold until Celestine passed out. He regained consciousness and began struggling as the cops tried to place him in a restraint device. Then Celestine stopped breathing. The coroner found his death was caused by “mechanical obstruction of respiration (‘suffocation’)” due to “carotid restraint hold by police while resisting arrest.”

The records did not include evidence that the department ever conducted a use-of-force review. Antioch Police Chief Tammany Brooks said in an email that his department does “review” deadly incidents, but doesn’t document any findings unless it receives a formal complaint or investigators think a policy might have been violated. Celestine’s asphyxiation death didn't prompt such an investigation, nor did eight shootings by Antioch cops from 2014 to 2018, he said.

Brooks at first agreed to an interview but then decided to postpone indefinitely. He wrote in an email that he “recalled a number of our policies are currently undergoing review and updates, including policies potentially involved with this topic.”

Pittsburg police have since changed their policies; the department now reviews all deadly-force incidents and documents findings. Addington said in “the vast majority of the cases we identify something that we could maybe look at differently.”

Before this policy change, Pittsburg, like most of the other agencies found to lack internal investigations, simply relied on criminal investigations done by the county district attorney.

For example, when police in the Monterey County town of Marina were asked for investigative records of a deadly 2015 shooting, they responded by email that internal investigations are “conducted by the District Attorney’s Office,” not the police department.

But prosecutors have a different focus: whether an officer committed a crime.

Then-Monterey County Assistant District Attorney Anne Michaels made that clear in the report she wrote on the 2015 Marina shooting: The DA’s scope “is not to advise best practices for law enforcement in the field, but rather to determine whether any officer committed a crime beyond a reasonable doubt.” She found the Marina officer was legally justified when he shot and killed a man who’d just stabbed his wife.

But even a legally justified shooting can provide vital tactical lessons, said former internal affairs investigator Gregson. Sometimes it’s learning how deadly force might have been avoided, or identifying what went right.

Telling officers fresh from a violent situation that they made good decisions can be “huge” for them, Gregson said, and is “an important thing for officers to be able to hear.”