A written appeal against extradition was turned down in July. Sarao's hearing will take place on Friday 14th October in London. Should he lose the appeal, he will have to stand trial in the US, where he faces charges of "unlawfully manipulating, attempting to manipulate, and spoofing" in the S&P 500 e-mini futures contract on CME.
The CFTC alleges that Sarao's trading - specifically his layering of the orderbook - "contributed to an extreme...order book imbalance that contributed to market conditions that led to the Flash Crash". The DoJ has filed a similar complaint against Sarao on counts of fraud, manipulating prices, and violating CME rules.
Mr. Sarao's chances of winning the appeal seem low given that historically the UK has complied with around 90% of US extradition requests. Perhaps he should have based his operations out of Venezuela, which has no extradition treaty with the US.