How can false positive or false negative tests for GSR happen?

False positive or false negative tests for Gunshot Residue (GSR) can occur due to various factors. Contamination from environmental sources, such as exposure to gunshot residue in public spaces or handling firearms without discharge, may lead to false positives. Conversely, false negatives can arise if the residue is not collected promptly after discharge, if the individual washed their hands, or if the testing method is not sensitive enough to detect low levels of residue. Additionally, the presence of other substances can interfere with the testing process, leading to inaccurate results.