concurring.
I recognize that in every drug prosecution, the government must prove beyond a reasonable doubt that the contraband in question was indeed a controlled substance. Nevertheless, I am satisfied that, in the absence of some threshold showing by the defense in a particular case that there is reason to doubt the government’s chemical analysis, the discovery provided by the prosecution to . these appellees would be quite sufficient. I do not construe the opinion of the court, which I am pleased to join, as being to the contrary.