Jurors in the Gwinnett County trial of the alleged murdering mother-in-law heard from one of the ex-husbands of defendant Joanna Hayes--and he says she pulled a gun on him.

Hayes is accused of killing her daughter-in-law, Heather Strube, in April of 2009, moments after she and her estranged husband had swapped custody of their 18-month-old son in the parking lot of a Snellville Target.  Prosecutors say Hayes disguised herself by wearing a wig and mustache.

Stephen Strube, Sr. testified that when the couple were going through a divorce in the early 1990s, Hayes once held a gun to his head in an argument.

"It was right here," he said, pointing his index finger at the middle of his forehead.  "It was just a few seconds.  That pretty much ended the argument."

Earlier, attorneys for both sides argued over whether the jury should be allowed to hear the testimony.  Defense attorneys called it "character assassination" against Joanna Hayes.  Gwinnett Assistant District Attorney Dan Mayfield disagreed.

"The nature of the assault was identical to the assault in the murder, and this same weapon was placed to the head of the victim," said Mayfield.  He said the .38 caliber Hayes used to threaten her then-husband was the same gun she used to kill Heather Strube. The defense argued that no police report on the incident had ever been taken.

"You didn't call the police?" defense attorney Bruce Morris asked incredulously.

"No, sir," replied Strube, Sr.

Ultimately, the judge allowed the testimony.

Using a dramatic pause, Morris also asked Strube about his relationship with Hayes since he married her sister a few years ago.

"Your relationship with Joanna Hayes is...challenged?" Morris asked.

"That would be one way to put it, yeah," said Strube.

Monday, prosecutors played a tape of a recorded conversation Hayes had with her son in which he told her he had recognized her build and her walk from surveillance tape at the scene of the murder.

"Mom, why did you do it?'' he cried emotionally.  Hayes denied that she had.