I had to think about how it could be plausible to anyone, and then I remembered what my late father (a chemistry major who later worked as an industrial engineer) used to tell me about working in chemistry labs. Sometimes you have to sit around and wait while an assay runs, but I suppose an efficient person (who has enough equipment) could run more than one assay at a time, and monitor each result in turn. I have no specialized knowledge about what a normal rate of doing tests would be in a well administered state crime lab.