I've been an opponent of correctional privatization since retiring over 20 years ago. The for-profits do little if any background screening, have a huge turnover rate, and low paid employees are a massive conduit for contraband. You can't stop it entirely, but you can reduce it substantially.

In the CCA/CoreCivic prison holding Alaskans in Pinal County, AZ, I found the warden who was previously a major at GEO Group, had killed another driver when he was drunk, years earlier. The assistant warden got busted when a cache of heroin was found taped under his dashboard in the prison parking lot. Another guard had murdered his wife while working for CCA in Minnesota, then they rehired him in AZ after he fled the jurisdiction. He was brought back and convicted of manslaughter. CCA leased a pen in California to the state, which said it would hire any CCA guard (for considerably higher pay) who could pass a background check and the C.O. boot camp. 75% of them couldn't. 

Any more questions?