These two activities use solving crimes as a context for physics teaching.
Speed cops uses the premise that a driver is suspected of speeding. The car has been caught on CCTV. can pupils show whether or not it was speeding? Is the driver correct to claim that she was slowing down? This activity uses Windows Moviemaker (free to install) or a similar application and requires you to make a video clip of a car travelling along a stretch of road (e.g. the playground) where pupils can safely make distance measurements.
The second activity uses refractive index matching – the wonderful phenomenon whereby glass can disappear in a liquid with the same refractive index – to solve a burglary.