Left inset: Kierstan Morgan. Right inset: Jiler Hainsworth (Bonneville County Sheriff's Office). Background: Tautphaus Park in Idaho Falls, Idaho, where cops say Kierstan Morgan attacked a 16-year-old girl after being told by her boyfriend Jiler Hainsworth that the teen was flirting with him (Google Maps).
An Idaho teen unleashed a "brutal beating" on a 16-year-old girl playing basketball at a park after being told by her boyfriend that the victim was flirting with him, cops say.
Kierstan Leann Morgan, 19, of Idaho Falls, is facing a charge of felony aggravated battery after attacking the teen at Tautphaus Park in Idaho Falls in May 2025, according to court documents obtained by East Idaho News.
Morgan was at the park with her boyfriend, Jiler Hainsworth, who was 17 at the time, when the victim says the young woman began accusing her of flirting with Hainsworth. The teen was playing basketball with a group of friends when Hainsworth told Morgan that she was flirting with him, the court documents say.
Video obtained by police shows Morgan allegedly setting upon the teen while yelling and threatening her. The victim tried to walk away but Morgan punched and pushed her to the ground, mounted her, then started grabbing her head by the hair and slamming her face into the ground, according to cops.
Police say the victim believes she passed out during the assault, as she doesn't remember much of what happened after being pushed to the ground. She was taken to a local hospital and treated for an injured mouth, loose teeth, face swelling, bruises and abrasions on her head, face and arms.
The court documents describe the attack as a "brutal beating," with Hainsworth allegedly telling bystanders he would hurt them if they stepped in, East Idaho News reports.
Hainsworth was identified through the fight footage; when police questioned him about what happened he was wearing the same clothes he allegedly had on in the video. He was reportedly very rude to cops and claimed he didn't start the fight, per police.
Hainsworth was charged with felony aggravated battery, felony witness intimidation and misdemeanor assault after being arrested in early February.
If convicted, Morgan will face a possible 15-year prison sentence while Hainsworth will face up to 20 years in prison. Hainsworth is due in court on Feb. 27 for a preliminary hearing. Morgan is scheduled to appear in court on March 10 for a pretrial conference. They're both currently out on bond, according to online court and jail records.