1. If you are not sure search the whole topic then focus on a part that intrigues you.
2. Whilst choosing your question include a factor... in my case it was religion
3. Also choose a time period if applicable or initiate the debate or argument
'Is the Death Penalty morally wrong?'
'Is the Death Penalty a fair punishment?'
'What impact does the Death Penalty have on serious crime rates?'
'Does the Death Penalty benefit society more than rehabilitation?'
Something like those? It is a very interesting topic, nice choice. One of my friends did it for her EPQ.