Presumptive vs confirmatory test
A presumptive test (Reinsch for heavy metals, Marquis for opioids, Trinder for salicylates) is fast, cheap and class-specific, used to triage caseloads. A confirmatory test (LC-MS/MS, GC-MS, ICP-MS) identifies the exact molecule and quantitates it. An Indian FSL report does not name a poison on a presumptive result alone.