And in at least five cases, he convinced female prison employees to have sex with him or do other illegal favors.
In each of those cases, the female corrections employees were caught, shamed and forced out of a job, according to documents detailing an investigation by Montana prison officials and obtained by The Associated Press after an open-records lawsuit.
The female officers described Murphy as the aggressor, even as the predator.
But that makes no difference in either state or federal penitentiaries, where prison employees - male or female - are the violators if they have sex with inmates.
A Justice Department study shows that cases like Murphy's are common: Female staff are more often implicated than their male counterparts in prison sexual misconduct. While many cases could be considered consensual, incarceration experts and female prison guards say the problem is much more complicated.
In some cases, the women reported that they couldn't say no to the inmate out of fear, or were afraid to go to a co-worker out of shame at what had happened. One small mistake often led to something else.
Experts say there is a culture of silence in the prisons that makes it difficult for female guards to come forward with problems before they spin out of control.
Documents detailing the state investigation into Murphy's liaisons show he even convinced his therapist to have sex with him, and was able to arrange one-on-one meetings with her even though prison officials knew of his past history with female workers.
Cover-up charges were filed against one of the female prison workers. Murphy, 36, faced no charges. He is serving time for theft, forgery and other charges.