A Lansing man has admitted to the 2008 strangulation of the 77-year-old woman who had raised him since he was 2.

Anthony Duane Thomas pleaded guilty but mentally ill to a second-degree murder charge in the killing of Ruby Thomas.

The 21-year-old said during the hearing Wednesday in Ingham County Circuit Court that he strangled his adoptive mother in her home on Aug. 4, 2008.

As part of an agreement with prosecutors, Thomas is expected to be sentenced to 13{ to 23 years in prison.