Surrounded by dozens of judges, fellow lawyers, relatives and admirers in a packed courtroom in Towson, John J. Nagle III was sworn in Tuesday as a Baltimore County circuit judge.

"Above all, I will be fair and just," promised Nagle, whose appointment forced him to end his longtime partnership in a Towson law firm and who several times has been voted one of Maryland's top attorneys by his peers. As he concluded his remarks, Nagle received a standing ovation.

Even with three decades of experience litigating all manner of cases and rising to the upper reaches of his profession, Nagle admitted to a mild case of nerves with the approach of his ascension to the bench.

"It's daunting to the extent that I can appreciate the seriousness of the matters that will come before me," Nagle, 55, said in an interview last month.

A past president of the Baltimore County Bar Association, Nagle said he was conscious of the "responsibility and trust" placed in him by Gov. Martin O'Malley. He added that he would have to adapt to "looking at things the way a judge does versus looking at things a trial lawyer does."

O'Malley announced Nagle's appointment Dec. 2 along with that of prosecutor S. Ann Brobst, who was sworn in two weeks later. In a letter read aloud at Nagle's investiture, O'Malley described him as "patient and well-grounded" and "smart, hard-working and prepared."

Another former prosecutor, Sherrie R. Bailey, was sworn to the same bench May 26. A fourth vacancy remains to be filled. All the new associate judges will have to run for 15-year terms in this fall's elections.

As of Tuesday, Nagle ceased being president of Bodie, Nagle, Dolina, Smith & Hobbs, although his name remains for now on the firm's building on West Susquehanna Avenue. While there, he specialized in mass tort litigation and practiced in business and commercial law, trusts and estates, and bankruptcy law.

"I liked being in a courtroom, and I liked working the cases up," he said. "It's a good background for what I'm about to do."

Nagle predicted that it would be hard to part ways with his firm after 28 years. "It's bittersweet in a lot of ways," he said. "It's really going to be difficult to leave something that I've helped grow and people I've enjoyed working with and cases I've handled. And it's sweet in the sense that it's a new job and a whole new life."

While he would not describe himself as authoritarian, Nagle said, "Basically, I mean business." He said he has "a very even temperament."

Nagle grew up in Towson's Wiltondale neighborhood and attended high school at Loyola Blakefield. His wife, the former Elizabeth Bagli, grew up in nearby Stoneleigh. Their three children helped Nagle place around his shoulders his first black judicial robe.

His mother, Eleanor, who was born in Wales, is 81 and attended Tuesday's investiture, as did his father-in-law, the retired sportscaster Vince Bagli. The new judge's father, John J. Nagle II, died last year.

Nagle graduated from the College of the Holy Cross, in Worcester, Mass., in 1976 with a major in history. He earned his law degree from the University of Baltimore in 1980, and was a clerk for Baltimore County Circuit Judge William R. Buchanan from 1978 to 1981. Buchanan, long since retired, also attended the ceremony.

"John's a rocker," said a fellow attorney, Keith R. Truffer, referring to Nagle's membership in The Mighty, Mighty Barristers, in which he sings and plays guitar. Composed, as the name implies, by a quintet of lawyers, the group was founded some 13 years ago and performs classic rock songs, mostly at attorneys' events.

"They've drawn favorable comparisons to the Rolling Stones, and John himself to Mick Jagger," Truffer said. He added that while some judges might quote the Greek or German philosophers, Nagle will take his inspiration from the Beatles' John, Paul, George and Ringo.

When Nagle's turn to speak came, he looked to his wife and quoted a Beach Boys song: "God only knows what I'd be without you."