The trial of Kaitlin Armstrong, 35, accused of murdering elite cyclist Anna Moriah “Mo” Wilson in May 2022, is under way. The sensational case, which prosecutors say is one of a love triangle gone bad, has riveted the close-knit cycling community and the trendy city of Austin, Texas, and has been featured on “Dateline.” 

Ms. Armstrong, who fled the country after the killing and was eventually discovered living under disguise in a small Costa Rican yoga town, claims she is innocent and the victim of a “nightmare” of circumstantial evidence. 

A rising star in the world of cycling, Wilson was supposed to have her entire career ahead of her. The Vermont native was even considered a potential future Olympian, but those dreams came crashing down when she was shot several times at a friend’s home at Austin, just before a race she was favored to win.

“The last thing Mo did on this earth was scream in terror,” a Texas prosecutor, Rickey Jones, told jurors in opening statements on Wednesday. “Those screams are followed by: Pow. Pow. Two gunshots — one to the front of the head, one to the side of the head that hits the index finger as it passes. You won’t hear any more screams after that.”

The defense attorney, Geoffrey Puryear, describing his client as a “woman trapped in a nightmare of circumstantial evidence,” said there was no footage showing Ms. Armstrong at the scene of the crime “despite there being tons of cameras in the area.” Accordingly, Ms. Armstrong has pleaded not guilty to the murder charge, which could result in a 99-year prison sentence.

In addition to the murder charge, Ms. Armstrong faces a federal charge of unlawful flight to avoid prosecution. Investigators say she sold her vehicle for $12,000 and left the country using her sister’s name, email, credit card, and passport following an initial meeting with police.

After 43 days, federal authorities eventually found Ms. Armstrong at the tiny yoga town of Santa Teresa, Costa Rica, where prosecutors allege she spent $6,425 on surgery to change her appearance, cut and darkened her hair, used several aliases, and tried to work as a yoga instructor.

“She would have no reason to know about any [arrest] warrant. You will hear Kaitlin is passionate about traveling and passionate about yoga,” Mr. Puryear said.

Authorities also say Ms. Armstrong tried to escape from two officers who were bringing her to a medical appointment from jail on October 11 by running away and attempting to climb a fence. Those actions led to another charge — this time for felony escape, which is punishable by up to 20 years in prison.

Yet how exactly are Ms. Armstrong and Wilson connected in the first place? The answer lies in what prosecutors say was a star-crossed love triangle between the two women and a top-ranked gravel racer, who was sponsored by Red Bull and other products, Colin Strickland. According to an affidavit released shortly after Wilson’s death, Ms. Armstrong split with her longtime boyfriend, Mr. Strickland, for a brief period in which Wilson became involved with him. 

On the day of the shooting, Wilson and Mr. Strickland reportedly went for an afternoon swim at Texas’s oldest swimming pool, followed by dinner. Mr. Strickland told investigators he dropped Wilson off at the friend’s house, where she was later found dead.

When police spoke to Ms. Armstrong the day after the killing, they showed her video surveillance that investigators said showed a vehicle matching the one she drives pulling up to the house where Wilson was staying just one minute after she had returned to the home from hanging out with Mr. Strickland.

Mr. Jones claims Ms. Armstrong, who lived with Mr. Strickland at the time, searched for information about Wilson in the days and hours before the killing, including through a workout app called Strava, which uses GPS to track a person’s location during workouts. On the day she was killed, Wilson reportedly logged a bike ride on the app that began and ended at the friend’s house where she had been staying.

After searching Mr. Strickland and Ms. Armstrong’s home following the shooting, investigators said they found a 9mm handgun that belonged to Ms. Armstrong. Police later said the potential the gun was used to kill Wilson was “significant” after comparing shell cases.

The case has had major implications for Mr. Strickland, who lost his endorsements over the killing.