What should I include in an presentation about Capital Punishment?

I'm against it, so I'm giving you a couple reasons why I am:

1) Cost - Research the difference in the cost of a capital trial compared to the cost of a non-capital trial. And with everything else involved, you will find that it is much, much cheaper to have a regular trial and sentence a person to life than it is to have a capital trial and sentence the person to death. (I'll leave you to find the exact numbers, which varies from jurisdiction to jurisdiction).

2) Mistakes - Since it's founding in 1992, the Innocence Project has helped free 227 people wrongfully convicted of the crime they were convicted of, including 20 people who were on death row waiting execution. And most people sentenced to die have their death penalty overturned on appeal, and they serve life without parole instead.

These two you should easily be able to find statistics and actual cases for your report using the US as an example. The other reasons I'm against are just my opinion (life serves the same function by removing the person from society, and that it's a form of vengeance, nut justice).

You have an answer from Mutt that mentions cost. This is only relevant to the USA, and does not belong in a British presentation about the subject. When the UK used the death penalty, a capital trial was exactly the same as a non-capital trial, and only three appeals were ever allowed. Execution was always set for three weeks after sentencing, traditionally to allow the prisoner three clear Sundays to make peace with God. This could be extended to six weeks at most to allow for the appeals. So we never had a death row because nobody was ever awaiting execution for that long.

For an interesting reason against it, look up Harold Shipman and Fred West. They both committed suicide in prison rather than face a life sentence. Is capital punishment really the easy way out? There is also Ian Brady, who keeps campaigning to be allowed to starve himself to death rather than go on living pointlessly, but there is no way he will be allowed to. If you really want to be nasty to someone, isn't it actually harsher to lock them up for life? Those three thought so.