When cops break the law, they do more than commit a crime — they undermine the public's trust in our justice system.

Society makes the rules we all must follow, and gives police officers wide-ranging powers to uphold them, with deadly force if necessary.

They are the last ones you want to see if you make a mistake and the first you call in an emergency.

For most of us, police officers personify law and order — and their bad behavior can shake our faith in both.

Bad cops are rare, we believe, but they can sow seeds of doubt about their honorable colleagues. Like it or not, citizens see the uniform — and one rogue officer can sully it for all.

Springettsbury Township Police Chief Tom Hyers understands this.

Even though he doesn't believe his officers use drugs, he also doesn't think the people they serve and protect should take his word for it.

Random drug testing for officers has been a goal of his since he was hired several years ago, and he worked with his command staff, the police union and township officials to craft a policy.

It goes into effect July 1.

Hyers is proud of his department for supporting the effort and said it reflects on the officers' professionalism and integrity.

"This is not only happening in Springettsbury, but all over the country," he said. "I just want to make sure that we have a drug-free police force, which I fully believe we have. And I want to make sure the citizenry has faith in our officers."

Springettsbury is following West Manchester Township, which began random drug tests for its officers about five years ago — at the officers' request.

"They have no problem doing it because ... they're not doing anything (wrong)," West Manchester Chief Arthur Smith Jr.

Like Hyers, Smith said the policy reinforces the public's trust in the department.

Given officers' work relies on that trust, we're surprised there's no law mandating drug-testing of Pennsylvania police officers.

Since there isn't, departments like Springettsbury's and West Manchester's deserve extra credit for taking the initiative.