Humans can always tell someone's sex at a glance
Helen Joyce said:
“Are you ever puzzled when you look at the people around you, what sex they are? Because I'm not. And it's no 1 feature. We're very, very good at recognising sex. It's a sealing attribute of human humans that we can tell what sex people are. 99.99 accuracy instantaneously.”
Most people do move through daily life without consciously struggling to identify the sex of those around them, so the claim that humans are naturally good at this feels like common sense backed by lived experience.
The 99.99 percent figure has no cited source behind it, and the actual research on sex perception tells a more complicated story: accuracy drops considerably when visual cues are ambiguous, which is true for a meaningful portion of the population, trans or not. What the claim is really doing is proposing that appearance should function as a gate, and the moment you apply that logic in practice, you are not screening for chromosomes or birth certificates, you are asking someone to make a snap judgement about a stranger's body in a corridor. Plenty of cisgender women with short hair, flat chests, or deep voices would fail that test on a bad day, and they would have no recourse. The people who pay for a policy built on this reasoning are not the people its supporters imagine.
What I said at the time:
“I think you know to boil down in 2025 in The United Kingdom, Great Britain that we're actually going to let peoples what they look like dictate which facility or service they're allowed to use by what they look like.”
Trans people and gender-nonconforming cisgender people who would face scrutiny, challenge, or exclusion based on subjective appearance judgements.