WhatsApp and Facebook messenger icons are seen on an iPhone in Manchester , Britain March 27, 2017.

© 2017 Reuters

After heated debate, the United Kingdom has just inched closer to adopting laws that would allow the United States to demand and obtain digital evidence – such as e-mails, texts, and chats – directly from companies that are storing it in the UK. This would do away with important rights protections under the existing treaty and policies, which require the UK authorities to scrutinize US demands for data on a case-by-case basis. The US has already similarly undermined rights safeguards by adopting the Clarifying Lawful Overseas Use of Data (CLOUD) Act, which Human Rights Watch opposed.

Some members of the UK Parliament tried to put the brakes on these developments, pointing out that the US could demand British-held evidence in US prosecutions that could lead to a death sentence – a punishment the UK government opposes.

Last Wednesday, the House of Commons responded by approving an amendment requiring the UK Home Secretary to ask the US – and any other country that allows capital punishment and hopes for a data-access agreement with the UK – for written assurances of the “non-use” of information from the UK in connection with a death-penalty case. However, the Home Secretary would not actually need to receive such assurances.

This is a problem. Even if Parliament strengthened the amendment to require assurances, the UK is poised to remove the most important means of ensuring US authorities stick to their rights commitments in every case: review and approval of each data demand.

Our research also prompts concerns that if the US does offer assurances that it won’t “use” data from the UK in death penalty prosecutions, it may decide for itself what “use” means – potentially in a way that allows it to take advantage of evidence from the UK, but conceal how it was actually used.

Through the practice of “parallel construction,” US police and prosecutors can avoid revealing the true origins of information in a criminal trial by deliberately re-obtaining it in some other way. And as we reported last year, we have specific concerns that the US government may employ a non-obvious definition of the word “use” to avoid revealing that it has taken investigative steps it prefers to hide.

As we have also urged regarding the UK’s potential extradition of ISIS suspects to the US, the UK should stand firm in not facilitating executions. This means preventing the US from grabbing UK-held data without strong, clear safeguards to protect against capital punishment. This isn’t an arcane debate about ones and zeros. It could be a life and death matter.