I know a few PDs, and I also worked in a court. The story checks out to me. I don’t think you’ll find a lot of PDs who will say cops and prosecutors regularly target genuinely innocent people. For the most part the job is to make sure all the boxes are checked and that the prosecution matches the actual crime.

Oh, you haven't met a lot of PDs, then. They'll tell you cops lie literally all the time and will make up evidence if they decide they don't like you. It's just easier and there's zero consequences for them if they're caught.

Do the cops “breaking procedure” know for certain if the accused are guilty? How can they?

Did you link the correct article? The author really says nothing about the legal system and is only reflecting that their 100% ACAB attitude maybe requires more nuance. This same author has written other pieces that plainly call the legal system an unfair joke (Eleven Words article specifically).

Regardless of any public defender's opinion, I am inclined to not fully respect opinions of people who are deeply embedded in the thing they have an opinion about, especially if it's in defense of the thing they're deeply embedded in. Humans lose perspective very easily, and especially when their identity is wrapped up in it.

I shared that to show that he has a somewhat odd background, not because it's directly relevant.

Yes, it's possible that insiders might have a biased view. However, in general, I do respect the opinions of people who have had experiences and write about them more than the comments of random internet strangers who, as far as I know, have no experience.