Fortunato N. "Fred" Perri Jr., a Center City criminal defense lawyer who worked with McGettigan as a city prosecutor and against him in private practice, ranked him "among the top prosecutors in the state."
"If Sandusky wasn't in enough trouble, he's got a much bigger headache now with Joe McGettigan," Perri said.
McGettigan, 62, brings a record as a veteran prosecutor who has tried homicides in seven jurisdictions.
Even Williams - the boss he left in June because of rumored personality and policy differences - called him "an excellent trial attorney with an impressive breadth of experience and incredible knowledge of the law."
McGettigan has experience in the state Attorney General's Office and two stints with the Philadelphia District Attorney's Office. He once was Delaware County's first assistant district attorney and a federal prosecutor in the U.S. Attorney's Office in Philadelphia.
He also has a record of convictions in high-profile cases, including the 1997 Delaware County trial of DuPont heir John E. du Pont in the slaying of Olympic gold-medal wrestler David Schultz.
"He's a formidable adversary," said Thomas A. Bergstrom, the Philadelphia lawyer who represented du Pont.
McGettigan, he said, is "very principled. If Joe doesn't agree with you, he'll let you know. If he's going to hit you, it will be a punch in the nose, not a stab in the back."
Born and raised in West Philadelphia, McGettigan is the grandson of a Philadelphia police officer and son of a lawyer who was district counsel for the U.S. Army Corps of Engineers in Philadelphia.
A high school basketball star who played several years in Europe, McGettigan earned his law license in 1982 and began an 11-year career with the Philadelphia District Attorney's Office.
Though McGettigan made his name as a homicide prosecutor, colleagues recall his strong interest in prosecuting crimes against children.
In 1985, he prosecuted one of the first sex-abuse cases involving a priest from the Archdiocese of Philadelphia: a 48-year-old cleric accused of abusing a 12-year-old altar boy. The priest pleaded guilty, was sentenced to 23 to 46 months in prison, and was deported to his native Brazil.
In 1993, McGettigan moved to the state Attorney General's Office, where he oversaw the probe into the 1993 state Senate election in Philadelphia's Second District. Twenty people were charged in an absentee-ballot scam, and fallout from the probe ultimately cost Democrat William Stinson his Senate seat.
McGettigan was recruited for the top prosecutor job in Delaware County by District Attorney Pat Meehan. In 2006, when Meehan became U.S. attorney in Philadelphia, McGettigan joined him as a federal prosecutor.
He left in January 2010 to become Williams' first assistant district attorney.
Described as an excellent writer, McGettigan interrupted his legal career after the du Pont case to try his hand in Hollywood.
He was a legal consultant in 2001 for Steven Bochco's short-lived Philly series starring Kim Delaney.
McGettigan also acted in a courtroom scene in one 2002 episode of the series. He played a police detective, not a prosecutor.
Contact staff writer Joseph A. Slobodzian at 215-854-2985, email@example.com, or @joeslobo on Twitter.