How Moussaoui jury must decide

Jurors in the trial of Zacarias Moussaoui are deliberating on whether he should be executed or spend his life in jail without the possibility of release.

Moussaoui, the only person tried in the US over the 11 September terror attacks, pleaded guilty in 2005 to plotting with al-Qaeda to fly airplanes into US buildings.

The jury has already found him eligible for execution after it accepted prosecution arguments that Moussaoui - who was in jail on immigration charges at the time - told lies to US agents that prevented them stopping the 11 September attacks.

The nine men and three women of the jury are now considering whether he should actually be put to death for any or all of the three capital charges against him:

• Conspiracy to commit acts of terrorism transcending national boundaries

• Conspiracy to destroy aircraft

• Conspiracy to use weapons of mass destruction (In deliberations during the first phase, the jury asked Judge Leonie Brinkema if an airplane constituted a WMD and she instructed them that it did.)

The defendant rejoices in all that pain - he told you that himself... there is no place on this good Earth for him David Raskin Prosecution Confine him to a miserable existence until he dies and give him not the death of a jihadist... but the long slow death of a common criminal Gerald Zerkin Defence Jury verdict form Most computers will open PDF documents automatically, but you may need to download Adobe Acrobat Reader. Download the reader here

The jury considers each of the three charges in turn.

For each charge, the jury first must determine whether government prosecutors have proven at least one of the following three things, known as statutory aggravating factors:

• That Moussaoui knowingly created a grave risk of death to one or more persons in addition to the victims of the offence

• That he committed the act in an especially heinous, cruel or depraved manner in that it involved torture or serious physical abuse to the victim or victims

• That he committed the offence after substantial planning and premeditation

If the jury decides that the government has not proven any of these three things, they must sentence him to life imprisonment for the charge they are considering.

However, if the jury rules unanimously that the government has proven at least one of them, they go on to weigh up possible aggravating versus mitigating factors.

There are seven aggravating factors which jurors can take into account if they decide that they apply, including:

• That his actions resulted in the death of approximately 3,000 people

• That they disrupted New York and the Pentagon

• That he has shown a lack of remorse

There are 23 mitigating factors which jurors can take into account if they consider them applicable, including:

• That a life sentence is a more severe punishment than death, or that it is the most appropriate punishment

• That Moussaoui seeks a martyr's death or that executing him would create a martyr for radical Islamic fundamentalists

• His unstable childhood, abusive father, experience of racism, and mental illness in his family

• That he is psychotic

• That his testimony as to his planned role on 9/11 is unreliable

• That his role in 9/11 was minor

• Any other mitigating factor that at least one juror wants to add to the existing list of 23

The process of weighing up aggravating and mitigating factors is not scientific - the jurors do not, for example, make their decision based on whether there are more applicable aggravating factors than mitigating factors.

For each charge, the jury must be unanimous in its decision that Moussaoui should face the death penalty or else they must sentence him to life in prison for that charge.