I am wondering how (if possible) the concentrations of certain drugs in a urine specimen can be used to indicate innocent/unknowing ingestion of a drug. I have an individual that tested positive for codeine (for which they do not have a prescription). The individual alleges that he received a tablet containing codeine without his knowledge. The results of his urinalysis generated 19,000 ng/mL of codeine. Given these results, would it be scientifically possible to justify unknowing/innocent ingestion.

Many panels use 150-300ng/ml metabolites as a minimum base. First you indicate 10,000 and then 19,000. Very substantial amount at 10,000 and 19 is almost 2X above that. 1 tablet won't do that.

Plus, it would not prove them innocent, the issue of why they took a pill, they did not know what it was from someone,

So they took it, thus they are guilty of taking it. Sorry,