We got a touching email Wednesday from a 30-year veteran of a Massachusetts police force. He wrote that his distinguished career was all tarnished ... after I reported (an) officer lying on the stand and going to the FBI." He was responding to an investigative story we published this week, Behind the Blue Wall, that documented how often police whistleblowers face retaliation for reporting misconduct. They have been threatened, fired, jailed, one was even forcibly admitted to a psychiatric ward. "I want to personally thank you for bringing this to light," the officer wrote. "You were able to write what I have experienced for the last 6 years. After reading this I took a deep breath and for the first time since this began I feel liberated from the stigma of being a rat, untruthful, discredited." Police covering for colleagues, and punishing those who don't, isn't new. But with this investigation, we wanted to quantify, for the first time, the extent of the problem and how it impacts the whistleblowers. Reporters sent out 400 public records requests and secured tens of thousands of pages of records. They found 300 cases in the past decade where an officer helped expose misconduct " a small window into how the system works. The vast majority of those cases ended with those whistleblowers saying they faced retaliation. "Whistleblowing is a life sentence," former Chicago undercover narcotics officer Shannon Spalding told our team. She faced death threats ... after she exposed corruption that led to dozens of overturned convictions.