Half a Knuckle

A unit of measurement a reporter invented for himself. No instrument can measure "how much a face has been changed," so he took the real bone structure of the person as he remembered it for a baseline and measured how far the features in the photographs had shifted — half a knuckle, one knuckle.

Its origin is crude. In the small hours, under the lights of a convenience store, at under 80 centimetres, he had looked at that face's brow ridge, eye sockets, forehead, eyebrows; standing in front of that photograph wall the next day, the brow ridge on the wall was half a knuckle lower than the one in his memory, the tips of the eyebrows slanted a little further down, the eye sockets shallower. The family's explanation was that he had lost 4 kilograms recently and his face had got longer. Losing 4 kilograms doesn't press a brow ridge down.

Finger joints are only good for a rough estimate. To leave a record you have to switch to the print's border as a scale, measure the brow ridge, the eyebrow tips, the eye sockets and the position ratios of the grey ring relative to the border, write the figures into the notes and align them with the file hashes; run the same set of ratios again the next day, and the day after, and you can see each item growing fainter by the day.

This ruler comes with a harsh precondition: whoever measures has to have seen the living person with his own eyes, and has to get there before his own memory has been touched. He looked at that face for about 12 seconds, at 03:19 in the small hours, the convenience store lights bright, at under 80 centimetres. By the following afternoon he was standing in front of that photograph wall, under 30 hours in between. A few days later and the baseline is no longer worth anything.

It sounds like a backyard method, and it is at present the only way to turn something as unsayable as the "overwrite" into numbers that can be recorded, compared and tracked. Whether the unit itself is accurate doesn't matter; what matters is that the same ruler is used every time. There is no column like this on a police missing-person form, and none on an equipment specification sheet — a deviation of this kind won't go into any format that already exists.

Afterwards, every time he measured, that set of figures was copied onto the same page, ranged alongside the timestamp, the location and the SHA-256 value, so that the next version of himself would have something to check against.