EASTON, Pa. – A Northampton County man accused of killing his mother’s boyfriend appeared in court on Tuesday.

Prosecutors allege Ryan Yaindl, 26, gunned down his mother’s longtime partner, Jason Derr, 52, in September.

The defense argued Yaindl was trying to save his mother’s life.

The benches behind Yaindl were nearly full, with family and friends as the West Easton Borough man appeared for his preliminary hearing.

Yaindl is charged with criminal homicide.

According to the affidavit, Yaindl’s mother had been dating Derr for nearly 13 years, a relationship described as “tumultuous”, alleging Derr of abusive behavior since the start.

Investigators said Yaindl had never gotten involved in the issues between his mother and Derr, until September 12th, when he heard his mother yelling for help downstairs in their home on the 100 block of Spring Street.

Court paperwork reads that Derr grabbed Yaindl’s mother by the head, pulled her off the recliner and dragged her, until he was confronted by Yaindl at the top of the staircase.

Derr then walked up the stairs and that’s when Yaindl allegedly fired gunshots, later saying “I think I killed him, call 911,” according to investigators.

“I don’t think I’ve seen a better case of self-defense,” said Gary Asteak, Yaindl’s attorney.

Asteak said his client and Derr co-existed, not friends nor enemies.

Asteak said the shooting was not premeditated and should not be treated as a first-degree murder case.

“He had to wake up to the horror of his mother being attacked by a ‘madman’, and then having to defend himself, and then having to defend himself with his back against the wall and a growling, grunting, ‘wild animal’, as he described it, approaching him and attacking him,” said Asteak.

There was emotional testimony from Yaindl’s mother. She recalled the moments leading up to her boyfriend’s death. 

A state trooper who responded to the scene also testified.

In a statement, the Northampton County District Attorney’s Office said:

“The Court today heard evidence that the defendant fired multiple shots and killed an unarmed victim. With that, the Court concluded that the evidence fully supported the charge of Criminal Homicide and held the case for trial. That was the only issue to be decided today. The case now moves forward as it should.”

Asteak said his next steps include filing a motion, challenging whether the case supports first-degree murder charges, and trying to get Yaindl out on bail.

Yaindl has a formal arraignment scheduled for November 5th.