Image copyright Facebook Image caption Lizette Andrea Cuesta "fought like a soldier", said the man who found her

A US teenager stabbed and left for dead on the side of a road used her last breath to implicate her alleged killers, police say.

Lizette Andrea Cuesta was found soaked in blood by UPS delivery drivers before dawn on Monday in a California town 50 miles (80km) east of San Francisco.

The 19-year-old's injuries were so severe the delivery employees initially thought she was missing an arm.

Police used Ms Cuesta's dying account to arrest a couple.

Image copyright Alameda County Sheriff's Office Image caption Daniel Lee Benjamin Gross, and Melissa Jill Leonardo are engaged, according to Facebook

Daniel Lee Benjamin Gross, 19, and Melissa Jill Leonardo, 25, appeared in court on Wednesday afternoon to be formally charged with murder.

Ms Cuesta had crawled nearly 330ft (100m) so that passing motorists could see her by the hilly roadside near Livermore, say police.

Investigators were able to measure the distance by the blood trail she left behind.

They said Ms Cuesta had been repeatedly stabbed and thrown from a car.

Image copyright Alameda County Sheriff's Office Image caption The roadside near where Ms Cuesta was found

Sgt Ray Kelly, of the Alameda County Sheriff's Office, told the San Francisco Chronicle the victim had given police a "compelling account".

"Her internal fortitude to stay alive and to fight is pretty remarkable," Sgt Kelly told the Chronicle.

"This young woman clung to life when she was left for dead and was able to live for another couple hours and get us that information."

Ms Cuesta was airlifted to hospital, where she died a short time later.

Investigators believe she willingly got into the car with Mr Gross and Ms Leonardo.

Image copyright Facebook Image caption Daniel Lee Benjamin Gross in a Facebook photo

Sgt Kelly said the victim was a friend of the couple, who are being held in the Santa Rita Jail.

Mr Gross and Ms Leonardo's Facebook pages indicate they are engaged.

A "tremendous" amount of evidence was recovered at the couple's home, Sgt Kelly told the Modesto Bee.

"The evidence and Lizette's statements to us helped make this investigation unfold very rapidly," he said.

He told the Chronicle it was very rare for investigators to obtain a "dying declaration" from a victim.

"A dying declaration is a very compelling piece of evidence that's recognised in the court to be very credible and reliable information," he added.

Richard Loadholt, one of the four delivery drivers who found Ms Cuesta, told KTXL-TV there was so much blood he could not tell the colour of her hair.

"She fought like a soldier," he told the news station. "Like a warrior."

She had been living in the nearby city of Tracy with her father, Ray Cuesta, at the time of her death.

He told CBS Sacramento he last saw his daughter on Sunday.

Mr Cuesta said he was proud the strength she showed even in death.

"She was always a fighter, she was always brave, strong, a leader," he said.