> Attorney General William Barr said in a speech last month that encrypted messaging services allow "criminals to operate with impunity." The cost of encryption is “ultimately measured in a mounting number of victims — men, women and children who are the victims of crimes, crimes that could have been prevented if law enforcement had been given lawful access to encrypted evidence,"
This disgraceful, emotionally manipulative statement is an obvious lie. Police/FBI/etc have have access to far more information about criminals than any point in history. The average person (criminals included) leaves behind an incredible amount of "digital exhaust". They should be able to build a complete pattern-of-life easily with 3rd party data (e.g. ad tracking), various side channels, and the massive amount of metadata[1] recorded every time criminals used their phone.
Of course, using all of that data to find a criminal requires actual detective work specific to each case. Encryption (especially on a phone examined after a crime) isn't preventing law enforcement from investigating crimes; it is, however, harder to automate. This anti-encryption argument is really about automated mass surveillance, not finding specific criminals.
[1] "We kill people based on metadata" https://www.youtube.com/watch?v=UdQiz0Vavmc