Jonathan Kirby, 56, entered his plea in a Van Nuys courtroom on Tuesday. He faces a maximum sentence of 38 years to life in prison if convicted.
The "NCIS: Los Angeles" actor and rapper confronted Kirby after finding him in the kitchen area of his home last Wednesday. LL punched the suspect several times and held him until police came and arrested him.
LL was not injured in the incident. Kirby suffered a broken jaw, nose and ribs.
Kirby has a lengthy criminal history, including manslaughter in Texas more than 20 years ago, along with burglary, escape and petty theft. Records show he was sentenced to six years in prison for the manslaughter charge, but was paroled the next year. In 1990, he was arrested on a prostitution-related charge in West Hollywood, and in 1995, he was convicted of felony residential burglary.
L.A. prosecutors say Kirby is a transient who has used different names over the years, and they want to treat him as a third-strike offender.