Future-proof

"Future-proof" was a legal term, applied to an individual whose death would have little to no impact on the causal nexus. In other words, their removal from the timeline would have no discernable impact on the planet's future. As the Referee put it, "Nobody will miss [them]."

In the 14th footnote to rule 4398, in the rulebook for the Hunt which came to Earth, selected targets such as Alex were identified and approved by a third party as future-proof. This served as ethical grounds to justify hunting this human: Alex was deemed inconsequential. (AUDIO: Moving Target)

The Eighth Doctor explained that the Web of Time was resilient. In some cases, events could be reshaped and could reflow. Some people, who had led quiet, obscure lives, and had no children, could safely have been made to die early. History could simply "blink and miss [them]". (AUDIO: The Zygon Who Fell to Earth)

River Song considered sacrificing Andrew Edwardson at The Bumptious Gastropod in order to save the Fifth Doctor, as Andrew was identical to him. (AUDIO: My Dinner with Andrew) In the end, Brooke 2 sacrificed Andrew to reverse the death of the Doctor without creating a new paradox, as his death would have little impact compared to the damaged caused by killing the Doctor early. Indeed, due to the death of the Doctor, the stars were going out. (AUDIO: The Furies)