When did the Ministry know about Death Eaters and their Marks?

[Brenda]

No: HPFGUIDX 100144

Hi everyone,

I just have a question about something that has been bothering me for 
a while.  It had occurred to me when I was re-reading Order of 
Phoenix; it was a part where Hermione said that once the Ministry & 
Daily Prophet believe Dumbledore wasn't so crazy, he will be able to 
prove Sirius' innocence.. "Sirius hasn't got the Mark for one thing.."

And I remember the trials that took place in Dumbledore's Pensieve.. 
Crouch Jr crying that he wasn't a Death Eater.. and Bagman denying.. 
Crouch Sr seemed adamant and uptight.. I was thinking, the Ministry 
could not have known about Death Eaters having the scar etched in 
their arms, otherwise it would have been a much simpler matter to 
distinguish the Death Eaters (wells, at least those who claimed that 
they had no association, as for those who claimed that they were 
under Imperius Curse, I don't know..).

But at the end of Goblet, when Snape showed Fudge his burnt Mark in 
the hospital wing, Fudge didn't seem surprised in any ways - which 
led me to believe that Ministry now knows about the DE's scar.  Does 
that mean the Ministry learned about it much after Voldemort's 
downfall?  If they did acquire this much-more-accurate way of 
distinguishing Death Eaters, why didn't they check Azkaban inmates to 
make sure that they did have the right people in prison?

This bothers me particularly since Sirius could have been cleared, he 
could have been FREE, and to top it all, he could have lived with 
Harry..  I have an issue with wrongly-accused people not getting 
enough compensation as they should, and when that kind of injustice 
happens to my favorite character.. not a happy combo..

Anyhoo, hope you guys all enjoyed the new HP movie!

Brenda