Russia says it believes the gas attack in Damascus on 21 August which left hundreds of people dead, was a "provocation" by Syrian rebels. Last week Foreign Minister Sergei Lavrov gave his US counterpart John Kerry what he said was evidence to back up this claim. It includes an investigation by a Catholic nun living in Syria. The BBC's Richard Galpin spoke to Mother Agnes.
Mother Superior Agnes Mariam de la Croix sprinkles blessings liberally over our conversation.
I've phoned her to request an interview about her strange role as an analyst of the chemical weapons attack in Damascus.
Mother Agnes's work normally revolves around the Catholic monastery of St James the Mutilated, which lies north of the Syrian capital. Although she is Lebanese, it has been her home for decades.
"God bless you my dear," she says once more as she puts the phone down. We have agreed to speak by video conference call the next day.
When, at the appointed hour, her face appears on the large screen in a TV editing suite in the BBC's Broadcasting House, she peers confidently into the camera lens on the computer in front of her, and helpfully tries to adjust the lighting and focus before answering each of the many questions I put to her.
It is not her first time on television.
In recent weeks she has become the focus of media attention because of her attempt to prove to the world that Syrian opposition activists fabricated the videos showing victims of the Damascus chemical attack.
She argues the horrifying scenes - of men, women and children either dead or dying from inhaling sarin gas - which caused such international outrage were stage-managed.
The videos formed an important part of the evidence used by much of the international community to argue that regime forces carried out the attack.
An attack on such a scale with so many victims in several different areas of the city, it was argued, could only have been the work of the regime.
But Mother Agnes claims to have carried out an exhaustive study of the videos and in a detailed report says she has found evidence of manipulation. (You can access the report here, but be aware some viewers might find images contained in it disturbing.)
For example, she claims the body of the same child can be seen in several different videos filmed in separate locations.
"Why should they take a corpse to many locations?" she says.
"It is evidence my dear... I am not a commission of inquiry, but for me it is sure. I have evidence that confirms there's been manipulation of the corpses."
Children without parents
Her report makes many more claims including:
- Ghouta, the main area to the east of Damascus which came under attack, was already "deserted", so why were there were so many civilian casualties?
- Why are so many children seen in the videos without their parents? There is "a flagrant lack of real families"
- Why are there so few women in the videos and why are so many people unidentified?
- Why is there so little evidence of burials?
In her most startling conclusion she alleges some of the people seen in the videos are in fact women and children abducted by rebels from minority Alawite areas of the country. President Bashar al-Assad and his family belong to this community.
"Some families of the abducted people contacted us to claim that some of the children presented as victims of chemical attacks are in reality their own children," says Mother Agnes.
"They recognised them and asked us to find out what happened to them."
After completing her report, Mother Agnes distributed it at the United Nations in Geneva.
The Russian government jumped on it, using it to bolster its argument that there were still strong reasons to doubt the Syrian government was responsible for the gas attack.
So how credible are the claims made by Mother Agnes which have been so eagerly seized upon by Moscow as it still tries to save the Assad regime?
"There's just no basis for the claims advanced by Mother Agnes," says Peter Bouckaert, emergencies director of Human Rights Watch, which has produced many detailed reports on Syria.
"She is not a professional video forensic analyst... we have found no evidence to indicate any of the videos were fabricated."
One by one, Mr Bouckaert rejected the claims, saying:
- There were tens of thousands of civilians trapped in the Ghouta area of Damascus, according to very regular reports received by Human Rights Watch
- Children were often sleeping in the basements of buildings in significant concentrations because of the intense shelling and that is why so many died (Sarin gas accumulates at low levels)
- The dead and those injured in the chemical attack were moved from place to place and room to room both at the clinics and ultimately for burial
- There were many men and women who were victims of the attacks. But there were separate rooms for the bodies of children, men and women so they could be washed for burial
- Almost all of the victims have been buried
- Human rights researchers have spoken to the relatives of Alawite women and children abducted by rebels. None of them said they had recognised their loved ones in the gas attack videos
While Russia's motives for promoting Mother Agnes's research, regardless of its accuracy, are obvious, what motivates her?
She is accused of being an apologist for the Assad regime - something she denies.
But she has accused the rebels of committing atrocities before.
It seems her motivation may be fear - that the Syrian government will eventually be overthrown by militant Islamist groups, jeopardising the future of the minority Christian community in the country.
She told me how she had travelled to areas under rebel control.
"I found a situation like Afghanistan," she said, "with Islamic tribunals... which decided if people would be beheaded, cut to pieces or raped."
Correction 4 October: The headline has been amended to make clear that Mother Agnes casts doubt on the footage of the gas attack, rather than the event itself.