There is something so interesting about the way Crouch described the torture of the Longbottoms as "a crime so heinous that we have rarely heard the like of it within this court" and what it says about Bellatrix.
I believe torturing two aurors until they literally lose themselves in their own minds is not easy to achieve. On the surface, it does tell us about the extent of the sadism and cruelty, but when you take Bellatrix's love for Voldemort into account, I think it says a lot more about her grief.
She believed he'd return, but that doesn't mean Bella wasn't grieving his disappearance for months (I'd guess at least four months since people were starting to feel safe again).
Also, Voldemort had been in power for a decade and I'm sure that court had heard about plenty of horrible things committed by the captured Death Eaters. And yet one of the worst crimes was committed by Bellatrix while she was grieving Voldemort...
I think Bella's grief and desperation played a major role in the Longbottoms' fate. I wouldn't be surprised if Barty was telling the truth when he denied the charges and that Bellatrix alone carried out the torture. I also think she used a lot of Legilimency on Frank and Alice, but that's another story.
