Just last week, two NYPD cops were indicted for evidence tampering for doing exactly that.
The indicted cops responded to an off-duty cop's DUI crash. They texted each other on their personal phones so as not to create a record. They positioned their bodycams so as not to capture the incident. At one point, one of the cops held the other's to make it look as if he was still standing there while he secretly called their supervisor. They then let the drunk cop drive away. Hours later, another officer found the car parked on the sidewalk. That officer did finally arrest him.
"These police officers did their job. We should not be here today," said union president Patrick Hendry, who accused the DA of targeting the officers. "He needs to support officers instead of going after them. Enough is enough."
To their credit, these charges came based on a referral from NYPD's Internal Affairs Bureau, though it was 4 years later.
Article: https://www.nytimes.com/2026/02/20/nyregion/nypd-dui-coverup...
The famous case of the cops arresting the nurse for not performing a blood draw without a warrant after a car accident is much the same:
The other driver in the car accident was a drunk off-duty cop who blew a red light and hit the patient (who later died).
Cops simultaneously scrambled to the hospital to get a blood draw there, while also delaying the draw on their buddy for hours.
Cop who performed the arrest was fired. And later sued the department for unfair dismissal, IIRC.