The Pennsylvania Attorney General's Office has taken over an investigation into the Bucks County Sheriff's Department, District Attorney David Heckler confirmed Friday.

Heckler said he decided to hand off the probe because of a potential conflict of interest. He made the request in an April 15 letter to the Attorney General's Office, he said, and it was granted April 26.

Heckler declined to discuss details of the inquiry. But after hearing the allegations, he said, he saw a possible conflict "because of the fact that I ran for office with the sheriff and am acquainted with various people who might be involved."

Heckler and Sheriff Edward "Duke" Donnelly ran on the same Republican political slate in the 2009 election.

Nino Tinari, a Philadelphia lawyer who represents a sergeant in the Sheriff's Department, said he had been told that the Attorney General's Norristown office would be convening a grand jury to look into the case.

"I contacted the A.G.'s Office, and they told me that there is indeed a grand jury investigation that will be conducted," Tinari said Friday.

E. Marc Costanzo, a senior deputy attorney general in Norristown, confirmed that his office would handle the case. He declined to discuss any particulars, including whether a grand jury would be involved.

Donnelly said Friday that he knew nothing about the attorney general's involvement.

"You know more about it than I do now," he said. "I never really got any notification" about the investigation, "so I couldn't really comment on it."

Heckler's letter was sent on the same day that the Doylestown Intelligencer reported that Tinari's client, Sgt. Gary Browndorf, had been called to testify before a Bucks County grand jury. That session, scheduled for the following week, was later canceled, Tinari said.

The department has been under scrutiny over alleged problems in certifying its deputies to carry firearms. According to Donnelly, a sheriff's lieutenant who served as a training instructor had let his own credentials lapse.

That, in turn, jeopardized the validity of dozens of certifications the lieutenant had signed, raising liability issues for the county. Donnelly said Friday, however, that a second range instructor had been present at the training sessions and that his signature had been deemed sufficient.

"Now, we have everybody qualified in 2011," Donnelly said. "If the qualifications weren't current in 2010, they are now."

In addition, Bucks County Commissioner Diane Ellis-Marseglia has reported getting many complaints of mismanagement, questionable spending, and political misconduct within the department.

She likened the misconduct complaints to behavior described recently within the office of county Register of Wills Barbara Reilly. In March, Reilly and three of her top assistants were arrested on political-corruption charges.

Ellis-Marseglia and other Democrats see problems in the register and sheriff's offices as issues in their campaign to win control of county government this fall after 24 years of Republican rule.

For Heckler, the recusal is a first. In his first 17 months as district attorney, he has rejected all calls from Ellis-Marseglia and others to step aside in controversial cases ranging from possible election fraud to pigeon shoots.

His name and Donnelly's appeared together on political yard signs in 2009, Heckler said, and they held at least one joint fund-raiser.

"We were definitely paired up," Heckler said, but "the campaigns weren't combined. Again, this is an issue of appearances.

"It would be easier if I could get into the specifics of the allegations," none of which accuses him of any wrongdoing, he said. "But that would not be appropriate; that's for the A.G."

Contact staff writer Larry King at 215-345-0446, lking@phillynews.com, or @kinginq on Twitter.