What crime did Lucius Malfoy commit?

What happened to the Death Eaters?

Imprisoned in Azkaban.

In Pottermore there the Malfoy family an indication of what happened after the war:

Abraxas' son Lucius rose to prominence as one of Lord Voldemort's Death Eaters, despite successfully evading prison following two attempted coups by Lord Voldemort. On the first occasion he claimed to have acted under the Imperius Curse (although many claimed he asked a favor from senior ministerial officials); The second time he presented evidence against other Death Eaters and helped capture many of Lord Voldemort's followers who had gone into hiding. His son Draco was saved by Harry Potter during the Battle of Hogwarts and currently lives on the family estate in Wiltshire.

So we have the arrest (and presumably incarceration) of high-ranking Death Eaters, but the Malfoys escaped prison by collusion. This was done through a web chat Deathly Hallows Bloomsbury confirms:

Georgina: Have Lucius Malfoy and all of the other escaped Death Eaters returned to Azkaban?

JKR: No, the Malfoys snuck their way out of trouble (again) because they worked with Harry at the end of the fight (albeit out of self-interest).

JK Rowling said in a 2007 interview with NBC that Harry and Ron had "completely revolutionized" the Aurors and, presumably, the Ministry's judicial systems. In Draco's case, I think Harry saw the ability to repent and might have been willing to offer Draco a second chance.

ETA: One thing that is clear from the top of the astronomy tower is that Draco is being forced and not acting of free will. I think the film showed this best (although the book has a very similar passage):

Dumbledore: Years ago I knew a boy who made the wrong decisions. Please let me help you "

Malfoy: I don't want your help. Don't you understand I have to do this. I have to kill you ... or he will kill me. "

I think this adds to the idea that Harry wants to give Draco a second chance.

I'm not sure what the Ministry's Justice looked like after Voldemort. I'm sure Harry would have made sure the execution was off the table (in the spirit of Moody and Dumbledore, if nothing else). From the same Bloomsbury chat:

Steph: Will Azkaban still use dementors?

JKR: No, definitely not. Kingsley would see to it. The use of Dementors has always been a sign of the Ministry's underlying corruption, as Dumbledore consistently claimed.

So we can conclude that Azkaban was still used as a prison, with more humane measures than before. Most Death Eaters would end up there.

And from the same chat we learn again that it wasn't just fully paid Death Eaters who received this treatment:

Pablo: What is toadface Umbridge doing now?

JKR: Nice to see that you like her as much as I do! She has been arrested, interrogated, and imprisoned for crimes against Muggleborns.

I would imagine Harry, Ron, and Hermione all pushing hard for this legislation and retribution (and were especially proud when Umbridge was convicted).

Awal Garg

How do you observe what JKR says in every interview?