The 38-year-old will return for sentencing on March 30, and he faces six years in prison.
An autopsy showed that the victim suffered 10 wounds, although Medina's attorney allegedly claimed Sutter was only stabbed once and dog bites on the body were mistaken for wounds from the sword.
Sutter, 36, was killed following an argument with Medina on January 31, 2015.
Last January, Medina was charged with the murder of Sutter following the fatal argument. They said when the argument became physical, Medina stabbed Sutter multiple times with a sword.
Medina was initially arrested shortly after Sutter's killing, then released after prosecutors asked for further investigation into the man's death, authorities said.
A spokesperson for the Los Angeles County Sheriff's department told The Wrap that the incident took place around 3:45pm.
The timing of this is all pretty awkward, because the Power Rangers movie - which Ricardo is not attached to - is about to be released. He also states Sutter was a friend, not a roommate, as has been reported in the past year.
The TMZ website reported a year ago the sword used had been a "Conan The Barbarian-style broadsword".
"Josh don't have that in his heart to attack anybody."
Ricardo Medina Jr.'s case isn't the first time an actor who appeared in the Power Rangers franchise has gotten in serious trouble with the law. His other acting credits include, CSI: Miami, Witchcraft, ER and Confessions Of A Pit Fighter.