As a degreed analytical chemist with 25 years in the pharmaceutical industry, I know that tests like this one are screening tests, and not definitive in any way.
To use them as definitive tests is unprofessional, ignorant and, hopefully, grounds for a lucrative lawsuit.
Any questions?
Just one: Why is a trained, experienced scientist posting retarded garbage on FR?
The field test was use as a screening test and not as a definitive test as you claim.
The officers in the field performed the field test, they obtained a (false as it turned out) positive result, so they arrested the suspect and sent the substance off to the lab for the definitive test. That result came back negative and so here we are.
Why is this so hard for you to understand?