Reddit reviews The Tough-on-crime Myth

>source please

There's mountains of evidence to suggest that "tough on crime" policies do little to actually tamp down crime rates (so, for examples, "broken windows" policies did next to nothing to reduce crime in New York; and crime rates plunged even after "stop and frisk" was abandoned by the NYPD); adding to this, we can recognize that places with relatively lenient judicial and law enforcement policies (say, Norway) have considerably lower levels of crime than places with relative harsh judicial and law enforcement policies (say, the US). Evidently, common sense would suggest the causal factor in crime reduction isn't (or isn't in any significant sense) a given political body's "toughness on crime."

But for more concrete evidence (of various levels of scholarly rigour) see here:

https://psycnet.apa.org/record/2011-20232-001

https://www.cmaj.ca/content/181/3-4/232

https://youthvoicejournal.com/2012/03/07/dunnette-m-and-winderdyk-j-2012-tough-on-crime-a-step-backwards-in-contemporary-social-justice-for-canada/

https://www.policyalternatives.ca/sites/default/files/uploads/publications/Manitoba%20Office/2015/09/Tough%20on%20Crime%20WEB.pdf

https://www.psychologytoday.com/ca/blog/crime-and-punishment/201804/why-punishment-doesnt-reduce-crime

https://www.thestar.com/news/canada/2010/03/15/toughoncrime_policies_dont_work_study_finds.html

https://www.bbc.com/future/article/20180514-do-long-prison-sentences-deter-crime

etc., etc.

So as far as sources go, you could read any of the dozens of scholarly articles or books written on the subject, but to be terse, let me just quote from the first linked article: "'tough on crime' policies are not supported by the scientific literature."