For those interested:
Reasons for refusing an extradition request
Reasons for refusing an extradition request, bars to extradition, are set out in both Parts1 and 2 of the Act, and also within multi and bilateral extradition instruments, and include the following (this list is not exhaustive):
'Double jeopardy'; a person must not be prosecuted or sentenced in respect of an offence that he has already been convicted or acquitted of.
Extraneous considerations; the request will be refused if the purpose of the request is deemed to be to prosecute or punish the person on account of race, religion, nationality, gender, sexual orientation or political opinions, or if extradited the person might be prejudiced at his trial or punished unfairly for any of these reasons.
Passage of time; the request will be refused if it would be oppressive to prosecute or punish the person for the extradition offence due to the age of the alleged offence.
Age of wanted person; extradition is not possible if due to his age the person could not be convicted of the offence in the United Kingdom.
Absence of speciality provisions; specialty is the principle that a person may only be dealt with in the requesting state for the conduct in respect of which extradition was ordered. Extradition instruments invariably include specialty provisions.
Earlier extradition of the wanted person to the United Kingdom; in order to permit extradition to the requesting state in this situation the United Kingdom must first obtain permission from the state that extradited the person to the UK.
Human rights; extradition will be refused if it would not be compatible with the person's rights under the European Convention on Human Rights within the meaning of the Human Rights Act.
Death penalty; a person must not be extradited if there is a possibility that the person will be sentenced to death. Extradition may be possible if the requesting state gives an undertaking that the death penalty will not be imposed.
Physical or mental condition; if it would be unjust or oppressive to extradite the wanted person on these grounds the extradition request will either be refused or adjourned until the condition improves.
http://www.cps.gov.uk/news/fact_sheets/extradition/