Forty-two years after he left the New York City Police Department, Frank Serpico never thought he’d still be fighting for police reform.

In the 1960s, Serpico was behind one of the biggest scandals in NYPD history. After being wounded in the line of duty, he testified before a grand jury and exposed widespread corruption throughout the department. He says that when he spoke out about the officers selling drugs, guns, shields and favors, he was shut out by the police force.

“I still have a bullet in my head,” he said, “and I was lucky to come out with my life.”

In 1973, Serpico's story was immortalized in the Oscar-nominated film that bears his name, with his role famously portrayed by Al Pacino. But these days, the 78-year-old stays out of the limelight. His interview with America Tonight was the first time he's spoken on camera in years.

We caught up with Serpico in Upstate New York about the spat between the NYPD and Mayor Bill de Blasio, the issue of excessive force in police departments across the country and why it's so hard to hold officers accountable when they shoot unarmed civilians. The questions and answers have been edited for brevity and clarity.

Looking at what's happening, not just in New York, but in Ferguson and across the country, what compelled you to come and speak out now about what's happening between the police and the public?

This is a national issue. In some places with little more than a high school equivalency diploma, you get a gun and a shield and you can take a man's life like that and not even be accountable. Where are we going here?

You’ve talked a lot and written a lot about the culture within the police force, and how that culture extends to the same body that then investigates their actions. Can you describe that culture a little bit?