I used to have no problem with the idea of Extradition. One of ours commits a serious offence in your country, leaves before he is caught, so you ask for him back in order to try him. That seems entirely appropriate for serious offences: murder, manslaughter, rape, grievous bodily harm.
But the UK now has extradition arrangements with the USA which seem contrary to ideas of natural justice in three respects.
First, you can be extradited to be tried for offences which were not committed - in any obvious sense - within the United States. In that case, why should you be tried there at all?
Second, you can be extradited for less serious offences where the whole process of extradition (not so very different from rendition) and pre-trial imprisonment (possibly lengthy) in a US jail is disproportionate to the offence committed. If the person is eventually found innocent, they will have already suffered materially and psychologically. In some cases, the US has successfully sought the extradition of people who have mental or physical health problems or who are elderly - in these cases, extradition itself can be traumatic. That would not be of consequence if we were talking about murderers. We aren't.
Third, the request for extradition comes from highly politicised US police agencies and the alleged crime is often enough one which elsewhere and among right-thinking persons would not be regarded as an offence or, at any rate, not a serious one. This appears to be true in the case of the Sheffield student, Richard O'Dwyer, who faces extradition for having created a website with links to file-sharing sites.
I conclude that the Extradition arrangements we have agreed with the USA should be scrapped. We should start again and confine our willingness to extradite UK citizens to those accused of grave offences against the person: murder, manslaughter, rape, grievous bodily harm. All the rest is very dodgy.