In case after case, officers said they had feared for their lives. And in case after case, prosecutors declared the killings of unarmed motorists legally justifiable. But The Times reviewed video and audio recordings, prosecutor statements and court documents, finding patterns of questionable police conduct that went beyond recent high-profile deaths of unarmed drivers. Evidence often contradicted the accounts of law enforcement officers.

Dozens of encounters appeared to turn on what criminologists describe as officer-created jeopardy: Officers regularly — and unnecessarily — placed themselves in danger by standing in front of fleeing vehicles or reaching inside car windows, then fired their weapons in what they later said was self-defense. Frequently, officers also appeared to exaggerate the threat.

In many cases, local police officers, state troopers or sheriff’s deputies responded with outsize aggression to disrespect or disobedience — a driver talking back, revving an engine or refusing to get out of a car, what officers sometimes call “contempt of cop.”