Section 39. (a) The department shall, free of charge, or the University of Massachusetts Medical School shall, under section 36B of chapter 75, make a chemical analysis of any narcotic drug, any synthetic substitute for the same, any preparation containing the same, or any salt or compound thereof, and of any poison, drug, medicine or chemical submitted to it by police authorities, as the department shall approve for this purpose; provided, however, that neither the department nor the medical school shall conduct such analysis unless it is satisfied that the analysis submitted to it is to be used in connection with the enforcement of law.

(b) A certificate by a chemist or analyst or other designated employee of the department or of the University of Massachusetts medical school of the result of the chemist's or analyst's or other designated employee's analysis, signed and sworn to by that chemist or analyst or other designated employee, shall be prima facie evidence of the composition, quality and, when appropriate, net weight of the substance or any mixture containing the substance.

(c) A signed certificate of drug analysis furnished by an analyst, assistant analyst or other designated employee of the Drug Enforcement Administration of the United States Department of Justice which conforms with the requirements of this section shall be prima facie evidence of the composition, quality and, when appropriate, net weight of the substance or any mixture containing the substance.