Cases like that of Mamana Bibi, a 68-year-old grandmother who, last October, was picking vegetables in the family field outside her home, with her grandchildren. No men of “fighting age” were anywhere near her. She was horrifically killed in a double strike, apparently by a Hellfire missile. A second volley of missiles was fired a few minutes later, gravely injuring some of the children who ran to the place where their grandmother had been. It is hard to know how a grandmother and her grandchildren could have posed an imminent threat to life. Hard to imagine also, how anyone could claim that in the immediate aftermath of an initial strike, a pilot thousands of miles away could determine who the people who ran to the scene of the incident were, and whether they were legitimate targets. In this instance, they were children who were maimed. These so called “rescuer attacks” are a grim signature feature of the drone attacks documented in the report.

International law prohibits arbitrary killing and limits the lawful use of intentional lethal force to exceptional situations. In armed conflict, only combatants and people directly participating in hostilities may be directly targeted. Outside armed conflict, intentional lethal force is lawful only when strictly unavoidable to protect against an imminent threat to life. In some circumstances arbitrary killing can amount to a war crime or extrajudicial executions, which are crimes under international law.

The USA continues to rely on a “global war” doctrine to attempt to justify a borderless war with al-Qa’ida, the Taliban or other “enemies” of the USA. It also claims that its drone strikes are extremely accurate based on vetted intelligence and that the vast majority of those killed have been linked to al-Qa’ida and its allies. The world has to take this on faith, since the US administration refuses to disclose key facts, such as details of who is targeted and on what basis. Certainly the findings of Amnesty’s research today put a significant dent in that faith.

The first rule about the drones programme is, apparently, that you don’t talk about the drones programme. Although that rule has not been universally adhered to, almost every element of the operation is surrounded in a veil of secrecy. The USA’s promise to increase transparency around drone strikes, underscored by a major policy speech by President Barack Obama in May, has yet to become a reality and the USA still refuses to divulge even basic factual and legal information.

This secrecy has enabled the USA to act with impunity and block victims from receiving justice or compensation. As far as Amnesty is aware, no US official has ever been held to account for unlawful killings by drones in Pakistan. The secrecy surrounding the drones programme essentially gives the US administration a license to kill beyond the reach of the courts or basic standards of international law. That secrecy extends to the involvement of other states. Amnesty is calling too for the UK government to refrain from participating in any way in US drone strikes that violate international law, including by the sharing of intelligence or facilities, or the transfer of specialist components, which we know has happened in the past.

The use of drones is rapidly becoming one of the big moral challenges of our time, and if we are not careful, their use will continue under the radar, and beyond the scope of public scrutiny. There are debates to be had about how technological advances are deployed and there needs to be accountability without exceptions. For now, we are dealing in the dark, without access to the quantitative data that experts need access to and reliant on compiling testimony from bereaved families like the Bibis who lost a wife, mother and grandmother when she was blown to bits from a pilotless aircraft in the skies. How common is that tale of woe? The truth is at the moment we really don’t know. It’s time for the US to drone up.

Kate Allen is the Director of Amnesty International UK. She fronts Amnesty’s campaigns which demand respect for women’s rights, stronger restrictions on the arms trade, the release of all prisoners of conscience, and an end to torture and the death penalty.

This essay originally appeared in the Independent.