A British victim of crime, on British soil, might reasonably expect their assailant to be tried in the British justice system. That was not Sarah Steele’s experience. US military police quickly took charge of investigating her assault by Jacob Wulfson in late 2023, and the airman was prosecuted in a US court martial – for a crime that took place off duty and off base, in an English city. Downing Street said on Friday that it was “very concerning” that the case never reached the Crown Prosecution Service, and the Ministry of Justice has said it will look into it.

Dr Steele waived her anonymity to speak to the Guardian about the “distressing and degrading” experience, casting light upon the little-known US military justice system and its use within the UK. Wulfson was convicted of strangling an intimate partner but acquitted of sexual assault and “aggravated sexual contact” by an all-male panel of air force officers stationed at the same base, RAF Lakenheath. Legal experts said the latter offence would probably have been categorised as rape in a British court. Dr Steele faced invasive, aggressive and lengthy questioning; her attacker chose not to testify.

More than 12,000 US personnel are stationed on 15 bases and facilities in Britain. Under a 1951 agreement, the US prosecutes them for offences committed while they were on duty, or against other US personnel, US armed forces’ property, or a dependant such as a spouse or child. That scope in itself is deeply concerning: the death of a British citizen in a collision off-base would still come under US military jurisdiction if the driver was on duty.

British police and prosecutors otherwise have the first option on investigating and charging American military personnel. In practice, however, US authorities appear to be claiming a much wider jurisdiction – and British authorities are falling in line. They are required to give “sympathetic” consideration to US requests to take over cases, and often allow the military authorities to do so, according to a US air force expert. The Guardian has identified scores of convictions in courts martial in the UK over the past decade, including for child sexual abuse offences, violent attacks and drink-driving. A significant number involved British victims and were committed outside US bases.

At a minimum, British authorities should be warier of passing cases to the US military, and more accountable and transparent when they do so. As Dr Steele has urged, police should seek the views of victim-survivors before relinquishing cases, and formally record and account for their decision to do so. That is especially important when cases occur off-base and involve those unconnected to the US military. There should be a central record of such cases, and their outcome. The US military publishes a docket of forthcoming courts martial, but while it lists alleged offences and subsequently convictions, it offers no further detail.

It’s easy to see how US military justice on British soil serves the interests of the US military. It’s unclear how it serves those hosting them. The current US administration is allergic to calls for military transparency or accountability, and disdainful of its allies. Yet its bases overseas are under increasing scrutiny, especially because of Donald Trump’s illegal war on Iran. In the long run, the US will find it hard to maintain public acceptance of those facilities without accepting greater scrutiny.