Each commissioner had his or her special clues for detecting Coloured blood, the result of rural superstitions.

A sniffer dog can detect blood even if it has been scrubbed off surfaces.

The test exposes a stool sample to a reagent that detects blood.

Electronic battery-operated monitors use a microphone to detect blood pulsing in the artery.

It is also used in criminal investigations to detect blood present with latent fingerprints.

The new test cannot detect blood that athletes have removed from themselves, stored and reintroduced just before competition.

They can detect blood from miles away: as little as one part per million of blood in sea water may be enough.

In the past, a diagnostic peritoneal lavage was often used to detect intra-abdominal blood, but this has largely been superseded by modern imaging.

If a home fecal occult blood test detects blood in the stool it is recommended to see a health professional to arrange further testing.