A Philadelphia teen killed his ex-girlfriend outside a SEPTA station last year. A jury is being asked to decide why.

There’s no dispute that 18-year-old Morgan McCaffery was stabbed and slashed to death by her ex-boyfriend outside a Montgomery County train station last year.

But as the trial for Gilbert Newton III opened Monday in Norristown, jurors were asked to choose between two narratives as to why. Was he a jealous, jilted ex who methodically plotted her July 2020 murder at the Meadowbrook SEPTA station in Abington? Or a despondent, suicidal teen who went there intending only to harm himself?

Those dueling theories were offered as Newton’s trial on first-degree murder began in Norristown before Judge William Carpenter.

McCaffery’s death — about a month after she graduated from Nazareth Academy, an all-girls high school in Northeast Philadelphia — came amid what advocates called an uptick in violence perpetuated by teens in relationships. And it became part of a larger trend of domestic violence in Montgomery County during 2020, including several murders.

Assistant District Attorney Gabrielle Hughes told jurors Monday that Newton, a Fox Chase resident, was jealous that McCaffery had moved on and was dating someone new. So he pleaded with her to meet him at the train station for one last conciliatory conversation, armed with two Ginsu knives he stole from his mother’s kitchen.

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In an overgrown parking lot, Newton repeatedly stabbed and slashed McCaffery and then sped away when a passerby spotted him, Hughes said.

“If the defendant couldn’t have her, no one could,” Hughes told jurors. “Ladies and gentlemen, please hold him accountable.”

But Newton’s attorney, A. Charles Peruto Jr., said the now 19-year-old brought the knives to use on himself, and only turned the weapons on McCaffery after she spit on him and mocked him.

Peruto said the young couple “played games with each other” and called McCaffery “highly immature” but stressed she didn’t deserve to die.

He urged jurors to find Newton guilty of manslaughter, a significantly lesser charge, saying that he was acting strangely for several days before the murder, making threats to harm himself.

Peruto also pointed out that Newton’s mother called Philadelphia police to turn her son in hours after McCaffery’s death, and promised that his client would take the stand to explain, in his own words, what happened that day.

» READ MORE: Philly teen stabbed ex-girlfriend to death at Montgomery County train station, DA says

Juan Vasquez, a landscaper who had been driving by at the time of the attack, testified he had spotted a tall, white man kneeling over McCaffery and tried to intervene. The man ran away, Vasquez said Monday, and sped off in a white Jeep.

A Montgomery County deputy coroner, Gregory McDonald, testified Monday that McCaffery had been stabbed at least 30 times, including one wound that punctured the right side of her heart. By the time police officers from Abington Township arrived at the scene, she had already died.

Hours later, police were summoned to Newton’s home by his mother’s 911 call. Parked outside the house was a white Jeep. Inside the blood-smeared vehicle, they found a sweatshirt stained with McCaffery’s DNA, according to prosecutors.

Philadelphia Police Officer Thomas Purcell told jurors that Newton appeared “out of it,” and repeatedly said that he “didn’t want to be in this world anymore.”

Newton, still wearing blood-soaked clothing, then confessed to the stabbing, according to Purcell.

The trial is expected to last through the week.