At the same time, five jurors were just as convinced that the doctor should have been found guilty of first-degree premeditated murder, agreeing with prosecutors that Oweiss had plotted to kill his wife because he was furious at her infidelity.
But after deliberating about 38 hours over six days, the jury of eight men and four women eventually reached unanimous agreement Friday and convicted Oweiss of second-degree murder.
Oweiss, 58, a gynecologist who practiced at Columbia Hospital for Women and kept private offices in the District and at his home, faces as many as 30 years in prison.
Montgomery County Circuit Court Judge S. Michael Pincus set sentencing for May 23.
The jury's lengthy deliberations heightened interest in a case that pitted a son's testimony against his father's assertion of innocence, and included a trial-stopping interlude when the defendant was accused of stealing an important piece of evidence in open court.
The jury was troubled that the murder weapon had not been found and by lapses on the part of police and prosecutors in handling a piece of evidence, two jurors said.
Several also were outraged at the father's attempt to blame his son, and they were upset at the defense's unflattering characterization of the victim as a domineering mother and unfaithful wife who had carped on her husband's looks and hidden his money in secret bank accounts.
At times, the deliberations became emotional, and some of the jurors still felt uneasy after their verdict was rendered, the jurors said. But they said a session with the judge -- who cleared the courtroom after the verdict to speak privately with jurors -- left them believing that they had done the right thing.
For example, the jurors said, Pincus told them about a second-degree murder plea bargain agreement that Oweiss had initially entered but then rejected before trial, and that there was evidence of other prior "bad acts" by Oweiss that could not be admitted at trial.
Because of court rules barring judges from commenting on cases, Pincus could not discuss the matter.
Oweiss killed his wife, Marianne, 49, after discovering that she had been having an affair while vacationing alone in Egypt in summer 2001. On Aug. 15 of that year, less than 24 hours after her return, Oweiss pretended to leave for work, then returned to the family's residence on Kentsdale Drive and beat Marianne Oweiss to death with a hard rubber mallet, prosecutors said.
Omar Oweiss,22, a senior at the University of Maryland, testified that he had been asleep upstairs with his girlfriend when he heard his mother scream. He ran downstairs, discovered her body and ran outside.
He said he saw his father holding a hard rubber mallet.
"She attacked me," the doctor said, according to Omar Oweiss's testimony. His father also asked the son not to call 911 until the weapon could be disposed of. Omar Oweiss said his father drove away in his mother's Jeep and returned minutes later. The mallet was never found.
In his testimony, Omar Oweiss also admitted initially lying and withholding information from authorities to protect his father. For example, he did not tell police at first that he had seen his father with the mallet, and he lied to authorities about the whereabouts of the red Volkswagen Jetta his father had been driving on the morning of the crime.
When deliberations began, three jurors wanted to acquit the doctor and two were undecided, jurors said. All five gave some credence to defense arguments that Omar Oweiss could have killed his mother during an argument because he, too, was angry at her for breaking up the family. Some jurors believed Omar was arrogant, untrustworthy and, at 6 feet 3 inches tall, capable of killing his mother, the jurors said.
"The defense did a very good job with these guys of convincing them that Omar was responsible. I saw what the defense attorney was doing was a sham," said juror Paul G. Robinson, 42, of Derwood.
After weighing and examining the evidence further --including a reenactment of how the 5-foot-6 doctor could attack his 5-foot-10 wife -- the jury rejected the defense theory, he said.
"I really liked Omar. He really impressed me as very smart, very savvy," Robinson said, adding that he believed Omar had lied before the trial, but not on the witness stand.
But the jury could not agree that the doctor had planned the killing, despite evidence that he had canceled his appointments that morning and instructed staff not to call his home. In addition, prosecutors argued that the manner of the attack -- in which Marianne Oweiss was struck in the back of the head at least seven times -- suggested an ambush.
To that end, prosecutors called William T. Vosburgh, director of the Prince George's County Police Department forensic services division and an expert on blood spatter, to testify about minute bloodstains on the doctor's clothing.
"That was the best evidence ever. That was the key, the smoking gun," said another juror, who spoke only on condition that his name not be used.
Oweiss, who was hospitalized with a heart condition during jury deliberations, heard the verdict over a telephone link to Suburban Hospital. Court officials had attempted unsuccessfully to set up closed-circuit television so that Oweiss could witness the verdict, but instead videotaped the proceeding.
After undergoing cardiac procedures, Oweiss was taken Monday to the Montgomery County Detention Center pending sentencing.