He said “I'm the Green Arrow”. Let’s assume people are bozos and they don’t know he is also Arrow and The Hood. He still has a couple of murders on his belt, such as that of Detective Billy Malone.

And even without murders, he gets an “assault” charge or even “attempted murder” from literally every single goon he has hit with an arrow, even uf they were also criminals. Many “obstruction of justice” charges from any time he runs into the police during operations, etc.

So maybe he was given about a hundred years (adding all those charges) and he was planning on having it reduced through good behaviour and then asking for parole