The trial of the man accused of being behind the massacre at a Colorado multiplex cinema in 2012 is due to begin.

Twelve people were killed and 70 injured when a man opened fire on movie-goers watching The Dark Knight Rises.

Former neuroscience student James Holmes will plead not guilty due to insanity, but prosecutors will attempt to secure a conviction and possible death sentence by proving he was sane at the time of the crime.

Dressed in body armour, Holmes is charged with walking into the cinema in the Denver suburb of Aurora, throwing tear gas canisters and opening fire.

When his automatic rifle jammed he began to use a shotgun.

It has taken three months to select a jury from 9,000 candidates who received summonses.

They had to fill out detailed questionnaires testing their views on crime, mental illness, their knowledge of the case and their attitude to the death penalty.

A total of 12 jurors and 12 alternates have been selected.

One of them is a survivor of the other infamous mass killing in Colorado, the Columbine High School massacre in which 13 people died in 1999.

One of the survivors of the Aurora shooting, Marcus Weaver, told Sky News how he had gone to the movie with his friend, Rebecca Wingo.

He described how they tried to hide underneath the seats, but he was shot in the shoulder and she was killed.

Mr Weaver says he has forgiven Holmes, but does not believe he was insane, calling the crime "calculated and heinous".

"Everybody knows right from wrong," he said. "Obviously I'm not an expert, but you're asking me what my opinion is, and how my family agrees with it? I feel he is guilty."

Mr Weaver will attend court and is due to testify later this week. Also in court will be Holmes' parents, who say he is not a monster but was in the grip of a psychotic event.