It’s entirely reasonable for the police to use field tests as a preliminary indication of an unknown substance but it always best to get a sample tested at a laboratory.
A recent case for Bericon involved a white powder that had tested positive for cocaine. However, the defendant denied that it was a controlled drug and asked for independent testing to be undertaken.
Subsequent analysis by Gas Chromatography Mass Spectrometry showed the substance to be free from controlled substances.
The reason for this false positive is unknown.
