Why did Dr Rajesh Talwar bludgeon his only daughter and his servant to death?
Through the trial the CBI has said that the Talwars found them together in Aarushi's room; at times they have said they servant and the teenager were in the midst of intercourse, at other times, that they were preparing for the act.
This was the "grave and sudden provocation" that Dr Talwar felt. It established the first ingredient any murder needs: its motive.
There is one vital circumstance the agency needs to prove in this scenario: Hemraj's presence in Aarushi's room. For if he wasn't there, there couldn't have been "grave and sudden provocation so how could the murders have taken place at all?
This is the question the defence asked as it began its final arguments in the trial court in Ghaziabad.
The Talwar's counsel Tanveer Ahmed Mir pointed that after more than a year's attempts (some of them ridiculously ham-handed), and 39 witnesses (many of them distinctly dubious) the CBI had failed to place a single piece of evidence to support the one pillar that held up its edifice: the agency has failed to provide anything that locates Hemraj in Aarushi's room on the night of the murders. No DNA, no blood, no fingerprints, nothing.
And yet, the whole story of the murders as told by the CBI rests on that one point: that the Talwar's saw their daughter with the servant--in her bedroom at midnight.
So how was this tale spun in the first place? And how did it attain the proportions it has today - as a 'credible' story; the obvious solution to the mystery behind the double murders.
The story behind the story is just beginning to be told in the trial court.
And it isn't pretty whichever way you look at it. If you are charitable, it begins with an enormous blunder. If you are not, then this is the result of something far more sinister.
A plan intended to send innocents to the gallows because flat-footed investigators had aided the escape of the actual perpetrators. If there wasn't a conviction, India's premier investigating agency would be shamed. (Not that it hasn't in the past, but that is another story.)
The theory that the Talwars saw their child in a 'compromising position' and committed the murders is laid out in a bizarre document called "Crime Scene Analysis based on photographs of the scene of the crime, post-mortem reports and other record of Aarushi-Hemraj murder case".
It was authored by a physicist called Dr M.S. Dahiya, of the Directorate of Forensic Science, Gujarat, on 26 October 2009, about a year and a half after the murders.
And it spins the story of the murders with a terrifying mistake as its premise. Dahiya writes: It has been attempted to be projected that Mr Hemraj was assaulted and killed on the rooftop of the flat of the Talwars. The presence of the blood of Mr Hemraj on the pillow in the bedroom of Ms Aarushi, however, negates that plea conclusively."
A year later, the CBI wrote a closure report for the case. There it admitted clearly Hemraj's blood wasn't found in Aarushi's room. So who had given Dahiya the one vital piece of non-existent evidence that built the case for the CBI?
And without any evidence of Hemraj being in Aarushi's room, didn't the case against the Talwars collapse?
Last year, upon reading his bizarre report, I spoke to Dr Dahiya about the faulty basis for his theory. He was evasive, said he couldn't remember who gave him what information and, of course, relied on the best defence available in such scenarios: "the case if sub judice, I cannot speak."
But Dahiya's blunders didn't end there, it builds on the mistake. He made the claim that upon seeing the photographs of the crime scene, he could divine whose blood was splattered on the walls. "The presence of two distinct spatters on the wall behind the headrest of Ms Aarushi's bed also goes to prove the contention of Mr Hemraj having been caused head injures in the room of Ms Aarushi itself."
This came from a man who admitted that he visited the crime scene well over a year after the murders. But then, if you can identify blood on the by photographs (who needs the science of DNA testing?), you could recreate anything.
Dahiya's 'analysis' is the turning point of this case. It is when the CBI began telling the world they had cracked it, and telling the world that the Talwars were guilty.
They have used the language of the report ever since, ad nauseum. Just one example: the phrase "dressing up" of the crime scene makes its first appearance in any record in this case in Dahiya's masterpiece.
It is a phrase the agency has used in every court, and repeated to every journalist. That the story itself was based on a lie to begin with is something that they have been in denial about through the trial.
The defence counsel pointed out on Thursday that two other testimonies, those of the post-mortem doctors were used to buttress Dahiya's arguments.
In his words, the two doctors committed nothing short of "medical blasphemy".
Readers of this column will probably remember the doctor who said under oath that erections have a life after death, and another, in whose memory, Aarushi's vaginal passage expanded with every retelling of his post-mortem report. Their integrity will be dissected on Friday.
Aarushi Talwar case: The end is near
Aarushi case: How the CBI framed the Talwars
Why CBI is reluctant to handover DNA evidence to Talwars