When the jury in Walter Reed’s 11-day corruption trial returned with a verdict about four hours after receiving the case Monday afternoon, observers and participants alike were caught by surprise. Former U.S. Attorney Harry Rosenberg said he had never seen such a quick verdict following a two-week corruption case.

Reed told reporters later that a short deliberation usually is good news for a defendant, but Rosenberg said his reaction was the opposite: He assumed a speedy verdict meant curtains for Reed.

Rosenberg, of course, was right. The jury of six men and six women found the former district attorney for St. Tammany and Washington parishes guilty on 18 of 19 counts ranging from conspiracy to mail and wire fraud, money laundering and lying on his tax returns.

His son, Steven Reed, was found guilty on three of the four counts he faced in the public corruption trial.

The jurors’ speedy conclusion, after hearing from more than 70 witnesses over two weeks and being presented with exhaustive financial documentation of Reed’s crimes, likely came down to a rejection of the former DA’s credibility, Rosenberg said.

The longtime politician, who held office for 30 years, spent nearly six hours on the stand Friday. He seemed to get off to a good start on direct examination, talking about his law enforcement career with the New Orleans police and engaging the jury. Even during a lengthy and tough cross-examination, he didn’t lose his cool.

But things still went south a bit, especially when Reed, 69, repeatedly claimed a foggy memory due to his age.

“There are only so many times you can tell a jury, ‘I’m not sure,’ ” Rosenberg said.

Matt Coman, a former federal prosecutor, said a jury might be willing to overlook a few of those lapses, but not too many. Reed also blamed other people for mistakes, including his secretary and accountant, another factor that likely hurt him, Coman said.

Coman helped lead another high-profile federal defendant, former New Orleans Mayor Ray Nagin, into similar tactical blunders in his 2014 trial.

The jury “almost summarily rejected (Reed’s) credibility and his proffered explanations across the board,” Rosenberg said.

Reed’s team struggled with a problem that Coman said is common to defendants in corruption and white-collar crime cases: the sheer volume of documentary and circumstantial evidence that is less vulnerable to challenges than most witnesses.

Reed’s attorney, Richard Simmons, seemed to vent that frustration when he complained at one point that he couldn’t cross-examine a sheet of paper.

The testimony of former Assistant District Attorney Leo Hemelt dealt perhaps the most devastating blow to Reed’s credibility. Hemelt told the jury that his former boss had asked him to sign a false affidavit saying Hemelt had been offered money to attend St. Tammany Parish Hospital board meetings, but had refused to take it.

The government said Reed pocketed $30,000 a year from the public hospital that was intended for the District Attorney’s Office. The fact that Reed sent Hemelt and another assistant DA — both on public salaries — to fill in for him at meetings was hard for the defendant to explain away. The fact that he asked a subordinate to lie about it was impossible to justify.

“This guy is pristine and totally ethical,” Jack Hoffstadt, another former Reed staffer, said of Hemelt. “It’s Walter versus him. Leo had absolutely nothing to gain for himself by testifying. All he got was to lose a job he loved.”

Hemelt said he was dumbfounded at Reed’s request and retired from the office shortly thereafter.

Other former DA staffers who testified for the defense, by contrast, gained enormously from their relationship with Reed, Hoffstadt said.

That was a theme the government sounded constantly on cross-examination, asking witnesses if they were part of Reed’s “inner circle” and questioning them about lucrative benefits he offered to favored employees.

The hospital portion of the case was viewed by many as the feds’ strongest material. Hemelt, along with hospital officials who testified they believed their arrangement was with the District Attorney’s Office, not Reed himself, cast doubt on Reed’s version of events.

“Once they (the jury) believe he is lying about that ... they don’t believe anything,” Hoffstadt said.

Reed was careful not to call Hemelt a liar, saying instead that his former employee was “mistaken” in his recollection. But he couldn’t contain his disdain, calling Hemelt a “Chicken Little.”

The prosecution’s success with the hospital charges left the defense with little choice but to focus on the other main prong of the case, the former DA’s misuse of his campaign fund.

Reed’s team worked hard to paint his use of money for lavish dinners, restaurant gift cards, parties and floral arrangements as typical — and legal — political activity. After the trial, Reed expressed amazement that spending campaign money on flowers was viewed as criminal behavior.

But the money that Reed spent, and the things he spent it on, likely hurt him with jury members who don’t have that type of lifestyle, Rosenberg said.

The defense was almost forced to call Reed to the stand, Rosenberg said, noting the large number of prosecution witnesses — 57, compared with 14 called by the defense.

While juries are told a defendant’s decision not to testify should not be held against him, many defense lawyers say juries routinely do so anyhow — especially when the defendant, like Reed, has a high public profile.

Both Rosenberg and Coman characterized Reed’s decision to take the stand as a calculated risk.

But Simmons, his attorney, wouldn’t speculate after the trial about whether Reed’s testimony hurt him, saying only that juries are unpredictable.

Follow Sara Pagones on Twitter, @spagonesadvocat.