Former Braintree detective charged with allegedly using Flock, other police tools to harass his ex

A now-retired Braintree police detective is facing a criminal harassment charge after he allegedly misused department technology — including Flock license plate readers — to harass an ex-girlfriend. 

Mark Sherrick, 55, retired in April 2025 amid an official investigation into his conduct, Braintree officials said in a statement. 

“The Town’s investigation, conducted by a third party, revealed that the former Detective misused police resources, including license plate queries, for a personal matter unrelated to a legitimate operational or investigative reason,” they explained. 

Braintree officials declined to comment further on case specifics, but charging documents allege Sherrick harassed his ex-girlfriend in a monthslong campaign “which seriously alarmed and would cause a reasonable person to suffer substantial emotional distress.” 

According to court documents, the woman told police Sherrick “had stood in her backyard during early morning hours following their breakup, driven by her residence even though there were only four residential homes on the street, used his police department issued cell phone, tablet, and cruiser for personal matters, and used a GPS tracking device on her vehicle to track her whereabouts.” 

An investigation into Sherrick’s emails confirmed that he was receiving GPS tracking alerts to his official department email address, the court documents allege, and the alerts purportedly matched the ex-girlfriend’s movements. 

Boston 25 News further reported that Sherrick used the police department’s Flock Safety camera system to track his ex’s license plate more than 1,000 times following their breakup in 2024. 

Records from the state’s police oversight authority, the Peace Officer Standards and Training Commission, indicate sustained allegations that Sherrick conducted an improper query of a town employee, used police resources to see who an unidentified individual was going on dates with, and placed a GPS device on someone’s vehicle to track their movements, among other claims. 

The POST Commission lists Sherrick’s status as “restricted,” indicating that while his certification remains valid, he is not currently authorized to serve in law enforcement because he is no longer affiliated with a specific agency.

Sherrick is scheduled for arraignment on the criminal harassment misdemeanor Sept. 29. 

Flock license plate readers have come under increasing scrutiny following recent reports that dozens of law enforcement officers nationwide have used the technology to spy on significant others, exes, or their exes’ new partners. 

Last month, the Stow Police Department disabled its Flock system and placed an officer on leave after the officer allegedly used cameras and other police databases to look up someone he knew personally. Police in New Bedford likewise suspended their use of Flock after an officer was accused of using the cameras to track her ex-girlfriend. And Lynn police placed two officers on leave after an audit of the department’s Flock system uncovered a “concerning pattern in some searches.” 

Braintree said it is “committed to upholding the highest standards of conduct for our police officers and ensuring the proper, responsible use of all law enforcement tools to maintain the public’s trust.”

Abby Patkin is a general assignment news reporter whose work touches on public transit, crime, health, and everything in between. She has been covering the Lindsay Clancy murder case since January 2023.