Walsh would not comment on whether there were more suspects. The Minneapolis Star Tribune reported that police are seeking other suspects and have evidence they believe is related to Porter's death.
Authorities declined to describe Washington's role in the beating.
Porter, a three-time All-America, is fifth on Villanova's all-time scoring list and first in rebounds. He played for Chicago, Detroit and New York during his NBA career. After overcoming a cocaine addiction, Porter settled in the St. Paul area and had been a probation officer for Ramsey County since 1995.
He was found severely beaten in a north Minneapolis alley on May 19, and died a week later, at 58, at a Twin Cities hospital.
Police said Porter was last seen in the evening of May 18 at his St. Paul home.
Washington was on probation in the past after being convicted of possession of crack cocaine, but Porter was not one of her probation officers, said Chris Crutchfield, spokesman for Ramsey County Community Corrections.
Her file was closed in June 2004, meaning she was no longer on probation.
The Star Tribune reported that Washington was convicted last year of furnishing alcohol to a minor.
Two rewards totaling $25,000 have been announced for information leading to the arrest and conviction of people connected to his death.
A funeral Mass in Porter's honor will be held tonight at the Villanova chapel. *