A Sangamon County judge has sentenced a man to 30 years in prison after he pleaded guilty to fatally strangling his girlfriend.

27-year-old Daniel Mueller was sentenced for first-degree murder Thursday in the death of 25-year-old Kayla Dillon in 2012.

Sangamon County State's Attorney John Milhiser says the plea deal was appropriate based on the evidence, Mueller's limited criminal history and his past diagnosis of mental illness. He says Mueller's lawyer could have used those factors to win an acquittal, a conviction on a lesser charge or a shorter sentence.

Prosecutors say Mueller strangled her in a house they shared and her body was found inside. Dillon's relatives say they had been dating for a few months at most.