Every day, tens of thousands of children around the world wake up behind bars.
Jensen is currently pursuing an appeal against his sentence
As part of a three-part series, Vera Frankl examines the fate of some of the young people locked up for life in the US state of Colorado.
Over 40 of the children currently behind bars in Colorado have no hope of ever being released. They were sentenced, while still under 18, to life without parole - in violation of international human rights law.
"After we got convicted, I guess I was still in shock," says Erik Jensen, who is one of these.
" But once the initial flurry is over, it's just despair. You feel like anything I do is for nothing."
When Jensen was 17, he helped a friend of his to cover up the murder of his own mother.
Jensen's friend had suffered years of physical and sexual abuse before the murder, including being raped by his own parents, although jurors trying Jensen were not told that. He was sentenced to life without parole.
Jones's family say he has changed massively in prison
"Once the prosecutor says that child is going to be filed on as an adult, that's the end of the story. Once that happens, no judge can stop it, no legislator can stop it, it just goes," said Jensen's father Curt.
"And the rest of society doesn't realise that we've changed the laws in this country, so that there is no other country that matches it in terms of what we do to our juveniles. None. Zero. In the world."
Thirty years ago, it was almost unheard of for children under 18 in the US to be tried and sentenced as adults.
But that changed after an upsurge in teenage violence across the country in the 1980s.
More than 40 states adopted laws which made it easier to try children as adults.
Tougher penalties were also introduced, which often included mandatory sentences for certain crimes.
In Colorado, this has meant children as young as 14 have been jailed for life. Some have been sent to Limon prison, 70 miles east of Denver, which has a reputation as one of the toughest jails in the state, the scene of riots, rapes and murders.
For nine years it has housed Trevor Jones, a one-time petty criminal and drug dealer who was jailed at 17 when a con trick went badly wrong, resulting in the accidental shooting of another youth.
As with the Jensen case, the local district attorney chose to try Jones not as a juvenile, but as an adult.
Although the jury accepted that the killing was accidental, Jones was found guilty on charges that, in Colorado, carry a mandatory sentence of life without possibility of parole.
"The attorney general kept arguing, 'this is a tragic case, but the law's the law'," said his father John.
"There's a problem with the law. If nobody cares that it's tragic on both sides, if nobody cares what really happens, these laws just don't make any sense."
Once a child is charged with a crime, the district attorney or prosecutor usually has just 72 hours to decide whether that child should be tried as a juvenile or as an adult.
And many in Colorado argue there is nothing wrong with that.
Among them is Dave Thomas, head of the Colorado District Attorneys Council.
He said his "underlying belief" is that the prosecutors use good judgement when they look at these cases.
"Yes, there is a huge difference between treating them as a juvenile and treating them as an adult.
"I think you have to believe that a public official will make good choices."
But Mary Ellen Johnson, director of the Pendulum Foundation - which lobbies on behalf of juvenile criminals - says she does not believe it should be down to a district attorney to decide a child's fate, as they are political figures.
"Other states give kids a second chance," she said.
"The difference between those other states and Colorado is that they go before a judge, and the judge says 'you're rehabilitatable, I'm going to stick you in the juvenile system.'
"In Colorado, the district attorney makes the choice. It's up to the district attorney who's voted in by the people it's a political office and so it's a slam dunk for a district attorney. He'll try these kids as an adult."
But Dave Thomas argues that it is precisely this that makes the system work.
"There is that public pressure, that's why they are elected, that's why they're in a position to make decisions," he said.
"They are the voice of the people, and so they need to be sensitive about how the public feels about crime and what should happen to crime.
"It's easy for people to say 'you're being very harsh.' But when I have to sit down with the victim's family and say, 'I know that your child's dead, but this guy's going to be out on the street in five years' - that's very difficult."