A Keelung court has convicted an elderly woman of scratching a man's car based almost entirely on a subtle change in how she moved her arm on security footage — a bad outcome for her, and a warning about how thin the evidence bar can be in property-damage cases.

• A woman was sentenced to 35 days' detention, convertible to a fine, for keying a car parked outside a temple last June.
• The footage never clearly showed the act — only that she was the sole person to walk past the car.
• The judge focused on her right arm suddenly shifting from a natural swing to a position close to the car body, at the same height as the scratch.
• Her defence was that failing eyesight made her mistake the car for a relative's, and that the scratch pattern did not match her movements.
• The owner admitted the car already had two older scratches in a similar spot, but reported it this time after friends said several cars had been hit.

Outlook: The ruling can still be appealed, and the owner is separately suing for damages.