A Santa Rosa man pleaded guilty Wednesday to three felony counts in the theft of more than $100,000 from his wife's 97-year-old grandfather.

Paul Alexander Tart, 29, could face up to five years in prison. He has a long criminal history in his home state of Illinois involving theft, forgery, burglary and drugs.

Deputy Sonoma County District Attorney Robin Hammond said the terms of Tart's plea agreement include the maximum five-year term.

Family members, including some of his four wives and their families, have been among his victims, according to interviews with relatives.

He was sentenced to Illinois state prison in 2007 for forgery and theft involving his then-dying mother, family members and court records said.

This time his victim was Leonard Key of Santa Rosa, who wondered earlier this fall why his bank account was overdrawn, authorities said.

Investigators learned that Tart had persuaded him to give him power of attorney and that Tart had been forging checks and otherwise emptying the account with unauthorized withdrawals, authorities said.

He also cashed in a life insurance annuity worth more than $51,000, and took that, authorities said.

Tart was scheduled to appear for a preliminary hearing on Thursday, but pleaded guilty Wednesday to one count of elder financial abuse and two counts of forgery, all felonies.

Because he took more than $100,000, his must serve his time in state prison, the District Attorney's Office said.

Tart is scheduled for sentencing Nov. 15.

Deputy Sonoma County District Attorney Robin Hammond said the terms of Tart's plea agreement include the maximum five-year term.