SALT LAKE CITY — The Utah Supreme Court has rejected a bid by a man convicted of killing a retired Brigham Young University professor in 2009 to withdraw his guilty plea.

The justices said in a ruling issued Wednesday that 30-year-old Benjamin Rettig’s guilty plea will stand despite his assertion that his attorney didn’t properly explain what he was agreeing to.

Rettig pleaded guilty in 2011 to aggravated murder and aggravated kidnapping in the killing of 70-year-old Kay Mortensen at his Payson-area home.

Rettig obtained a new attorney and tried to pull back his guilty plea three days before sentencing in July 2011. That was rejected, and he was sentenced to serve 25 years to life.

Before Rettig and co-defendant Martin Bond were charged, Mortenson’s son and daughter-in-law spent about five months in jail as suspects.