Nearly 33 years after a woman was repeatedly stabbed to death in her Uptown bedroom, a 58-year-old man has admitted to the crime, authorities said Thursday.

Robert Skogstad, of Edgerton, Kan., pleaded guilty to second-degree murder in the death of Mary C. Steinhart, then 22, of Minneapolis.

Hennepin County Attorney Mike Freeman said it’s the oldest cold case his office has successfully prosecuted.

Skogstad, the former caretaker of his victim’s apartment building, became a suspect thanks to a DNA hit as part of a cold-case investigation carried out by the Minneapolis Police Department and the county attorney’s office. He was arrested and charged in September 2012.

Skogstad, who remains jailed, will be sentenced Jan. 3 and is expected to receive 11 years and one month in prison, the length that sentencing guidelines called for in 1980 for second-degree murder.

In pleading guilty, Skogstad admitted that on Nov. 25, 1980, he stabbed Steinhart in the head, chest and abdomen. Steinhart’s sister found her dead on the floor of the bedroom inside the lower-level apartment in the 3200 block of Girard Avenue S.

Steinhart, a medical technician at a downtown Minneapolis urology clinic, had missed work for two days. Steinhart and her sister had moved from Grand Rapids, Minn., two years earlier.

Steinhart was last seen alive by two friends on Nov. 22, 1980. The next day, Steinhart missed a party she said she would attend, and after she didn’t show up for work on Monday or Tuesday, her employer called her family. Steinhart’s sister found her apartment door closed but unlocked.

Her body had roughly 25 stab wounds. Steinhart was also strangled, police said. Someone had covered her face with a pillow. There was no sign that anyone had broken in.

Skogstad had been a caretaker at the apartment building in 1978 and 1979 and still lived nearby at the time of the murder, according to police. He eventually left Minnesota, and a trail of public records shows he was convicted of crimes while living in Utah and California. His criminal record includes numerous convictions for purse snatching, theft, burglary and a sexual assault in California in the mid-1980s.

Star Tribune staff writer Matt McKinney contributed to this report.