They were giving preference to job candidates who said they wouldn't arrest fellow cops.

In other words, the Methuen police department was only hiring cops who promised to be corrupt and cover for their fellow corrupt officers.

According to the Boston Globe, 

A Civil Service Commission official wrote that he was dismayed to learn that the city gave higher points to applicants who said they wouldn't arrest a family member or an officer they knew, while docking points from who said they would.

"The City turned the interview process upside down," wrote Christopher C. Bowman, chairman of the Civil Service Commission, in a July 9 decision. "There is simply no valid basis to award the highest points to candidates who express a willingness to apply one set of rules to strangers and another set of rules to friends and family members."