Her two sons died in an overheated car while she was having sex in another vehicle.

A mother in the US is on trial for homicide after she allegedly left her two sons to die in an overheated car while she had sex and did drugs with a man in another vehicle.

Going back to November 2012 the Jensen family seemed just like many others in small town America.

Then tragedy struck with a head on collision that left them devastated – 26-year old Eric Jensen, father to two young boys and husband to Heather died instantly.

Court reports show that their marriage was anything but smooth with Heather on probation for a domestic violence assault against her husband.

Eric had told police Heather became violent after he confronted her about spending time with friends who supplied her with painkillers Vicodin and Percocet.

She was known to smoke marijuana and was undergoing court ordered drug testing- that she failed three times.

But photographs of happier times show a loving family living in the small Colorado town of Palisade – famous for its peaches and wines and picturesque mountain scenery.

No one could predict just how much more tragedy would hit this family  six weeks later.

On November 27, 2012 Heather had already moved in with another man – she is reported to have told this new live-in boyfriend she was taking her sons, William – aged 2 and Tyler – aged 4 to play in the snow.

She drove them to a ‘snow park’, where she met up with a male friend and left the two boys in her car, while she sat in the car of her friend smoking marijuana.

Court documents show that she firstly left the two boys in the car with the heat on and the doors unlocked.

But soon the eldest boy, Tyler opened the door.

His mother – disturbed from her friend’s car took him back to her own vehicle, where she gave him her phone to play with and then locked the door.

The children are said to have spent 90 minutes in the car, where an investigation revealed temperatures could have reached 60 degrees Celsius.

90 minutes while their mother – newly widowed – took drugs and had sex with this male friend.

After 90 minutes neither boy had much hope of survival.

Heather returned to her car. An emergency phone call reveals her shock at what she discovered.

Two-year-old William was not breathing and had no pulse, she also told dispatchers that four-year-old Tyler was barely breathing.

It was 90 minutes too long.

William died at the scene while his brother Tyler was airlifted to a near-by children’s hospital but he died a week later.

Initially Heather Jensen told police she had simply stepped away from her car for 10 minutes to smoke a cigarette with a friend.

This was soon disproven and she changed her story.

Both children died from hyperthermia, according to the autopsy by the County coroner. Hyperthermia is a condition, which causes extreme overheating in the body. The boys stood no chance.

In her trial, that started last week, prosecutor Danielle Lewis said, “Ms. Jensen created the situation that caused her children to die.”

The Denver Post reported that Heather Jensen wept throughout the opening statements. Her defence Lawyer saying that her actions should be assessed with regard to her low IQ, her youth and the fact her husband died six weeks earlier in a car accident.

“It was a tragedy, but it was an accident. It was not a crime.”

Now her husband’s parents, Robert and Diane Mathena, are seeking justice.

“It’s been horrible for us, a devastating year and a half that’s for sure,” Mr Mathena told CBS Denver. “Don’t want to see her anymore. I want her out of our lives.

Eric Jensen’s family had previously gone public with their wish that she face the death penalty for the two boy’s deaths.

The jury deciding the case was made up of 10 women and five men, but a judge on Friday removed one of the jurors from the trial when he found out she added a witness as a friend on Facebook.

The trial is expected to run for nine days.

We will keep you updated.