Rain seems to have a detrimental effect on scent availability when searching for evidence. Returning to the same area five minutes after the rain stopped, the dog easily found all the articles. Apparently scent is driven downwards during a rain and is less available to the dog. Scent will also be less available when the ground is colder than the air and the sun is not heating up the ground. This means that early mornings and cold, cloudy days are not the best times to search older crime scenes.
Dogs can detect objects which are under water.
Metal detectors will work through water. This fall one of our teams was called to an area where a deer was shot illegally by four shooters firing approximately 14 shots. Arriving three hours after the incident, the K-9 found 10 cartridges, most of them in deep, snow covered marsh grass, but one was under four inches of water. The team could have found the remaining four, but they felt they had enough evidence for the case. In another case, this same K-9 located a cartridge which was six days old and covered with snow.