LOS ANGELES — In a deal that spared him a potential death sentence, a man pleaded guilty today to murder for the stabbing deaths of his sister-in-law and her 6-year-old daughter in their Canoga Park home nearly five years ago.

Los Angeles Superior Court Judge Ronald S. Coen immediately sentenced Mario Estrada Ochoa, 36, to a pair of consecutive life prison terms without the possibility of parole for the May 14, 2010, killings of Martha Camacho, 21, and her daughter, Valerie.

Along with his guilty plea to the murder charges, Ochoa admitted the special circumstance allegation of multiple murders and using a knife in the commission of the crime.

“He’s a vicious killer,” Deputy District Attorney Beth Silverman told the judge.

Silverman told the judge that it was a “horrendous crime scene,” with Camacho suffering more than 30 sharp-force injuries as she was being chased through the family’s home. Ochoa posed the woman’s body in an attempt to make it look like a stranger had sexually assaulted her, the prosecutor said.

“He then murdered the only witness to this crime,” Silverman said of the 6-year-old, who was home for the day because she wasn’t feeling well.

The District Attorney’s Office had announced last year that it would seek the death penalty against Ochoa, who’s been jailed without bail since he was arrested in January 2011.