Comparison parameters are presented at various steps in the three stages of clandestine cocaine processing identified as the pasta lab, base lab, and crystal lab. Crude cocaine salts (alkaloid salts) are produced in the pasta lab by soaking the dry cocaine leaves in water and adding strong base, followed by the addition of a mineral acid to precipitate the salts. The purpose of the base lab is further purification of the alkaloidal mixtures by potassium permanganate oxidation of cis- and trans cinnmoylcocaine. Critical to this step is the stopping of the oxidation process, for it results in cocaine loss and the conversion of cocaine to N-formyl cocaine. In the last stage, the crude cocaine base is dissolved in ether and converted to cocaine hydrochloride with hydrochloric acid and acetone. Gas chromatography mass spectroscopy analysis of 100 random cocaine cases revealed that 60 percent of the samples contained detectable levels of N-formyl cocaine. Its absence only indicates that the permanganate oxidation steps was not employed. However, further investigation of processing impurities may be required to determine common batch origin. 8 figures and 44 references (Author abstract modified)