Former state Sen. John (Jack) Hart sailed through his second day of testimony at the trial of former Probation commissioner John O’Brien and two of his top aides. He acknowledged filing pension bills and amendments that would benefit employees at Probation, including O’Brien, but said the measures did not pass and were nothing unusual.

Prosecutors introduced a series of documents from Hart’s office obtained through subpoena that showed the senator filed bills and amendments between 2004 and 2006 that would have put Probation officials, including O’Brien and his top aides, into a more lucrative pension classification on par with front-line law enforcement officials. Hart, who represented South Boston in the Senate, testified that he filed the measures on behalf of a constituent named Bernie O’Donnell who worked at a Probation office in Clinton and was a member of a “union of sorts” at Probation.

Assistant US Attorney Robert Fisher tried to suggest Hart received encouragement to file the legislation from O’Brien himself by introducing a 2004 fax from O’Brien’s office to Hart’s chief of staff that included testimony O’Brien had given on the issue. But on cross-examination Hart testified that it was not unusual for an agency head such as O’Brien to contact state lawmakers or to testify on issues before the Legislature.

Prosecutors are trying to show that Hart and others in the Legislature placed people in jobs at the Probation Department and in return filed legislation benefitting the agency and its employees. They have charged O’Brien and top aides Elizabeth Tavares and William Burke III with mail fraud, conspiracy, and racketeering.

Hart testified that he filed his budget amendment with the Senate Ways and Means Committee, which was headed in 2006 by Sen. Therese Murray, who went on to become Senate President in 2007. He said that budget amendment and the other measures he filed did not get passed into law. He said he typically filed 40 to 60 budget amendments a year.

In testimony last week, Hart remembered almost nothing about his advocacy on behalf of people seeking jobs at Probation. On Thursday he said the prosecution’s claim that he sent 35 letters of recommendation for people seeking Probation jobs worked out to an average of two per year over his 17-year legislative career. “We wrote hundreds of recommendations each year,” he said.

He said some of the people he recommended for jobs got them. “Most times they were not hired,” he said.

Prosecutors went fishing on a couple fronts. They asked Hart about the husband of one of his aides, Joseph Jackson Jr., who worked at Probation, but drew no link between Jackson and any hiring activity. They also asked about campaign donations from Probation employees, but Judge William Young ruled that question out of order. Campaign finance records indicate Hart received 15 contributions totaling $1,800 from people identifying themselves as Probation workers, including $375 from Jackson.

Hart remained fuzzy about most hiring details, saying he may have written to Robert Mulligan, a chief judge of the state Trial Court, on behalf of people seeking court officer jobs. He also was shown a letter he sent in 2007 to Margaret Marshall, who at the time was the chief justice of the Supreme Judicial Court, on behalf of a man identified as James Pierce. Pierce was seeking a job at Probation. Marshall responded by referring Hart to O’Brien. Hart didn’t remember the Marshall letter, but said an aide probably mistakenly sent the letter to the chief justice.

Asked if success or failure in landing jobs for constituents affected how he voted, Hart replied: “Never.”