Nicki Minaj married Kenneth Petty even though he's a registered sex offender who served seven years for killing a guy.

The registered sex offender part of the equation -- which he got tagged with after being found guilty of attempted rape many years ago-- came back to bite Petty a few years back when he was arrested in California for failing to register as a sex offender.

He will be sentenced for the crime of omission on July 6.

Petty hopes to get house arrest.

However, prosecutors argue that Nicki's gated LA home is just too nice to serve his time in.  They want a 15-month sentence in a proper prison, followed by five years of probation.

So next month, we'll see where Nicki's registered sex offender husband will spend his next year.