Crane, the founding chief prosecutor for the Special Court for Sierra Leone -- an international war crimes tribunal that convicted Liberian warlord Charles Taylor -- gathered a dozen legal experts to draw up a "starting point" for discussions.
"Usually, the international community just sits back and waits and when a political solution is done and the killing stops, everybody scrambles to try figure out what to do," Crane told AFP.
"I thought 'Well let's be ready and have this on the shelf.'"
Working with the Syrian opposition, non-governmental organizations and staff at the University of Syracuse where he is now a professor, Crane's team has mapped out the atrocities committed in Syria since the war began in March 2011.
The catalog of horror stretches into three volumes and is growing.
Draft indictments have even been prepared against Syrian President Bashar al-Assad and his "top 10 henchmen," Crane said, adding that others have also been drafted for some opposition commanders, as well as foreign fighters.
He did not detail any of the indictments, stressing any charges would be up to the court's eventual chief prosecutor.
In the initial stages of the war, about 90 percent of the atrocities were being committed by the regime, but now Crane estimates that it's "about 50-50."
"First it was a civil war, it was bloody and problematic, but now it's gotten personal. And it's gotten bloodier, the longer this thing goes on, the less likely a peaceful transition will happen," he said.
'Not an academic exercise'
How any future court will be composed and the role of The Hague-based International Criminal Court (ICC) is still up for debate.
But Crane insisted the effort was "not an academic exercise."
"It's put together by seasoned practitioners who have been working for over 20 years in this business, looking at both not just the law, but also the practicalities, the politics and diplomacy of what it takes build a domestic court, a regional court or assist the permanent court," he added.
After two years of work, the draft blueprint says there was a strong feeling that any court "should be domestic, but with international elements," for example two Syrian judges sitting with an international colleague.
Its purpose "would be to prosecute those most responsible for atrocity crimes committed in Syria by all sides of the conflict when the political situation permits."
There's a strong preference for the court to be based inside Syria.
"We found in Sierra Leone that a court that sits right in the scene of the crime is much more effective," Crane explained.
"At the end of the day, we tend to forget this, these tribunals are about the victims and they have to be seen as such... It has to be right there so the people of Syria can see justice truly being done."
It could well be that the ICC could be called upon to try Assad -- although Syria is not yet a signatory to the court -- while lower-level officials may be brought before some kind of domestic or regional tribunal.
One of the thorniest issues will be whether the death penalty is retained. Under ICC rules, there is no capital punishment. And any international court would likely bar it too.
But many Syrians want it kept on the books.
"At the end of the day, which is a very Middle Eastern perspective, they want revenge," Crane said.
"The concept of an eye for an eye goes back thousands of years."
Crane has already briefed the ICC on the blueprint and it has been read with interest by officials at the US State Department, which says it wants to support the Syrian people in setting up accountability mechanisms.
"What's happened in Syria has shocked our moral consciences, whether that's chemical weapons or whether it's 100,000 people dead," a senior State Department official said.
Over the decades, various legal mechanisms have been adopted after conflicts in places like Rwanda, Bosnia and Iraq.
And while many Syrians are deeply committed to justice and reconciliation, the US official said, there are a lot of "varying opinions from Syrians on the inside and the outside."
"Because there are a lot of manifestations of criminal accountability for Syrians, understanding all of the pros and cons of each of those processes is incredibly important," the official added.
All agree though that when the time comes, how justice is handed down to those with blood on their hands has to be determined by Syrians -- the very people who have suffered the most.