Unethical Prosecutors Are Leading Cause Of Wrongful Convictions In California

Prosecutorial misconduct and eyewitness identification were the most common errors in the flawed homicide prosecutions. When broken down by type of error, prosecutorial misconduct accounted for more of the cost in our sample than any other type of error. 

By contrast, the most common errors in our sample were Fourth Amendment search and seizure errors, and judicial mistake. These errors were resolved relatively quickly, however, and resulted in relatively little cost.

From here.