Russian Extradition requests have been declined by the UK Courts for a number of reasons. The main ones are:
Breach of Article 3 of the European Convention on Human Rights, the right to not be tortured and be held in inhumane and degrading conditions. Russian prisons are in general not compliant with the European convention, so says the case of Ananyev v Russia 2012 (ECHR). They are appallingly overcrowded and the conditions which prisoner are held is in breach basic human rights. Whilst Russia has provided assurances that conditions are humane in many cases, none have yet been found to be genuine. The UK will not extradite where there is a real risk of Article 3 not being complied with, under section 87 of the Extradition Act 2003 which is concerned with human rights.
Breach of Article 6 of the European Convention on Human Rights, the right to fair trial. Many Russian extradition requests are made against powerful opponents of Putin and because of corruption at a local level. The interference with judges by state officials has led to many extradition requests being discharged on the basis that they will not receive a fair trial. The UK will not extradite where there is a real risk of Article 6 not being complied with, under section 87 of the Extradition Act 2003.
Corporate raiding – many requests are made as a result of corporate raiding and the abuse of the Interpol system to attack business rivals to takeover their companies rather than as genuine criminal offences. The UK will not extradite where there is evidence of political motivation of an abuse of the courts process under section 81 of the Extradition Act 2003, which is concerned with "extraneous considerations".