Wizard Barristers hasn't exactly been a series with a realistic eye for legal proceedings, but surely even in this world a defendant asking the subject of his crime to be his defence barrister is highly irregular?
Regardless, this is exactly the position that Cecil finds herself in at the behest of Makusu, although to her surprise he reveals that the reason for this is that he wants to make amends and admit all of his crimes, including those surrounding her death and her mother's subsequent trial, while she looks on. If this sounds too good to be true, then you'd be exactly right, and it soon becomes clear once the prosecution enter the scene that they're keen to push for many of the charges to Makusu to be dropped, to the point where they're even claiming that a fine would be sufficient punishment.
All of this comes to a head when he reach the trial itself, with Makusu insisting that he knows nothing of summoning magic, or why Cecil was unconscious in his apartment - when push comes to shove the true extent of his malice is revealed as he tries to frame Cecil for his son's death into the bargain, in the knowledge that there are no other reliable witnesses. Thankfully for our protagonist, Butterfly Law Offices have an ace up their sleeve, and in time-honoured courtroom drama fashion they burst in at the last moment to reveal this trump card; the one man who knows everything of Makusu's plan, starting six years previously. Then we have a courtroom battle sequence to close things out because heck, why not?!
While Wizard Barristers started quite strongly and certainly had its moments, it ultimately didn't really succeed in making the impact it might have hoped for - its take on courtroom drama was mostly terribly written to the point of being laughable (as depicted by this episode, which was ludicrous on many levels), some of the build-up towards its main story was equally bad, and its big action set pieces were too few and far between to save it. I don't want to be too harsh on the series as it did have a certain charm to it, and in places its action was stunning, but its intriguing premise could clearly have been so much more compelling given some a better plot and writing.