There was yet another dramatic shift in the emotional temperature at the Paris attacks trial on Tuesday, as two anonymous and invisible police investigators gave lectures on the history of Islamic holy war and the Syrian context of the 2015 massacres in the French capital.
It was like being back in university. The silent ranks of journalists tapped or scribbled their notes as two successive disembodied voices related the history of Islamic jihad from the year 750 to 2015.
The two witnesses, identified as 565SI and 562SI, are high-ranking officers in the police anti-terrorist intelligence structure, and their lives are at risk. Hence the need for anonymity.
Their testimony was relayed to the courtroom by video link, but all we saw of either man was a vague shadow. Their voices were clear.
Those voices outlined fourteen centuries of change in the understanding of "jihad," the "struggle" which the prophet Mohammed originally envisaged as an internal battle to live as a faithful Muslim.
The fourteen accused sitting in the Paris courtroom seemed to doze through it all. Given what we learned of their backgrounds in last week's investigation of the prisoners' personalities, it was difficult to imagine that history had had a major impact on the personal trajectory of any one of them.
But the objective of this mammoth hearing is to understand every aspect of the background to the murderous November night in which 130 people were killed and the 131st victim began his slow descent into depression and suicide.
Revisiting the battlefields
So we revisited the battlefields of Afghanistan, Algeria, Yugoslavia and Chechnya, noting how each of those conflicts attracted an "international brigade" of faithful foreigners who, if they survived, returned to their home countries with a high level of military skill and, in many cases, a dangerous determination to continue the war against unbelievers.
That murderous energy was channeled, notably by Osama Bin Laden and his Al-Qaeda network, resulting in terrorist attacks in east Africa, Yemen, the US, Djerba, Spain, London . . .
Until the civil war in Syria gave Islamic State the opportunity to attempt to establish an Islamic caliphate, and the focus shifted to the effort to create a sharia state.
France became a prime target. The country's colonial past, the perception of the republic as hostile to Islam, and the military commitment by the Paris government to the war in Syria, combined to ensure France a high place on the list of nations to be punished.
And punished she has been.
Mohamed Merah returned from Afghanistan to murder people in the southern city of Toulouse. There were grenade attacks against Jewish targets in the northern Paris suburb of Sarcelles. There was Charlie Hebdo, November 2015, Nice, Strasbourg, Samuel Patty, to mention only a few.
'The horror, the horror'
The appalling lives of those who volunteered to accept the rules of Islamic State in Syria were outlined by the second police witness.
Rape, brutality, murder and torture were part of the daily routine.
Robbers suffered amputation. Homosexuals were thrown from high buildings. Raqqa, the capital of the caliphate, was decorated with the severed heads of enemies and unbelievers.
"It was a bizarre world in which murderers and torturers were regarded as heroes. The opposite of normality," the police commissioner observed.
The trial continues.
Wednesday's hearing will feature the much-anticipated testimony by François Hollande, president at the time of the attacks, greatly criticised by survivors and bereaved families for the failures of his administration to protect French citizens.
