A state's attorney best known for prosecuting the Washington-area snipers was sworn in Tuesday as Maryland's first new attorney general in 20 years.

Montgomery County state's attorney Douglas Gansler, a Democrat, made national headlines during the 2002 sniper attacks in suburban Washington. He was criticized by some for deciding to prosecute Lee Boyd Malvo and John Allen Muhammad even after they were convicted in Virginia, an exercise some called a waste of money.

Gansler was the first to charge Malvo and Muhammad for the murders in his jurisdiction, but the case was wrested from him by federal officials who wanted a trial in Virginia, where they believed it would be easier to get a death sentence. After Muhammad and Malvo were convicted in Virginia, Gansler had them brought to Maryland for trials that he said provided insurance for the local victims' families.

Gansler also led the 1999 road rage prosecution of boxer Mike Tyson.

"I'll do my absolute best not to let you down," Gansler pledged after taking the oath of office. He said his top priorities would be tougher penalties for polluters and the creation of a state racketeering statute.

Gansler replaces J. Joseph Curran, 75, a fellow Democrat who has held the post since 1987. Curran's political career spanned nearly 50 years. Curran was a state delegate, state senator and lieutenant governor before being elected attorney general, one of only three constitutional elected offices in Maryland.

Curran's retirement from politics comes just two weeks before his son-in-law, Baltimore Mayor Martin O'Malley, becomes governor. When Curran announced his retirement in May, he denied that a potential conflict of interest played a role in his decision to step down. Observers, though, said Curran's retirement helped pave the way for O'Malley's victory over Republican Gov. Robert Ehrlich.

Curran told reporters Tuesday that he counted as major successes of his tenure Maryland's role in a multibillion tobacco settlement and his successful appeals to get tobacco retailers to curb advertising thought to attract young smokers.

"Hopefully when my grandchildren grow up they won't even be selling tobacco anymore," Curran said.

Curran said he may write a book, but wasn't sure if future plans included a temporary stint heading the Injured Workers' Insurance Fund, which he has said he wants to lead.

"I have a couple opportunities to do some teaching, and we'll see what else I can do," Curran said. "I'm just getting my second wind for my next career."

In Gansler's remarks, he referenced criticism that he was too zealous on the sniper case.

"We never failed to hold a criminal accountable in any major case," Gansler said. He said he would now turn his attention to consumer protections and quality-of-life matters, especially the environment.

"We're going to wage an all-out war on those who pollute our air and water," he said.

Gansler is the first of three new statewide officers to take office. O'Malley becomes governor Jan. 17, and Democrat Peter Franchot will become comptroller Jan. 22, replacing William Donald Schaefer.