A Police Officer’s View from Street Level: An informative and insightful interview with Sergeant Adam Plantinga of the San Francisco Police Dept. and author of 400 Things Cops Know: Street-Smart Lessons from a Veteran Patrolman (Quill Driver, 2014). “Being a cop hammers the compassion out of you. There’s a 90-10 rule in law enforcement: 90 percent of people are decent, 10 percent aren’t, and as a cop you deal with that 10 percent about 90 percent of the time.” Plantinga’s father is Cornelius Plantinga.