I do not get the idea of the defendents giving a speech at the end, especially when they have chosen not tobe cross examined during the appeal. It seems unfair that the prosecution get one shot at summing up to the jury, yet the defense in effect get three - the defense lawyer, and the two accused.
It also does not seem to add anything to the evidence for or against them, and seems to be purely emotive.
It's the defendant right to speak to the court in their own voice, in their own words. It is also their right to not take the stand and face cross examination.
In order to make sure that one right does not cancel out the other the defendant is automatically given "the last word" as a form of a personal statement, which given it is their neck on the line, that seems fair enough.
Unless a defendant decides to unexpectedly confess or reveal something bombshell like, it won't affect the verdict so much (you can't motive a sentence by writing, "well the evidence was crap/not bad, but actually when it comes down to it, he looked/sounded guilty/inocent and we're going with that", theynhave to go with the evidence that did/did not stand up to scruitny) as far as I understand it is more seen as an attempt in incur leniency in terms of jail time to be served should the defndant be found guilty.
I think, given it's the only time anybody will hear K and S speak whilst being held, without the lens of prosecution, defense or media colouring how and what they chose to say, its place is justified.
I think it may be a consitutional right actually