In regard to my column in the CHINA POST where I discussed this entire matter, I offer the following comments.
Regarding making application with the prosecutor: According to what the police were saying, I got the impression that this could take some time. It certainly did not seem to be “within 30 minutes.” It might be “within several days”. In the meantime, since you are being non-cooperative, I assume that you will be held in a holding cell with various other people, some of whom may have bad breath, body odor, etc.
Regarding the quotation: " . . . they suggested that if the person-in-question had just come back from a heroin party in Burma (for example), then all relevant evidence should be assembled, and he/she could then present it in a coherent fashion when called into court." I think that this comes across as rather sarcastic in English, although in Chinese it is certainly less so. But the point remains: Can you present a coherent case to prove that you did not use the drugs in Taiwan? That is the final issue, according to what I understood. If the drugs are in your system, then you are highly suspicious of being a Taiwan-based drug user. OK, fine, you say you are not. Prove it. I think that this is the bottom line, even though it is not very pleasant.
I think that in many instances there is no presumption of innocence here, although of course the Chinese do not interpret their laws and regulations that way. However, in terms of the actual enforcement, it often works out that if you are highly suspicious (due to any number of contributing circumstances), then there is a clear presumption of guilt.
If you really want to see some change in this kind of attitude among the officialdom here, then you and I should sit down together and discuss your sponsorship of a suitable “test case,” to get things fully clarified via the use of the court system.