specially concurring:
I concur in the majority’s holding that the evidence in this case was insufficient to prove beyond a reasonable doubt that the substance found in defendant’s possession was a controlled substance. The opinion falls short, however, in failing to hold that field tests currently in use, which seek to identify the composition of an unknown substance on the basis of a color change, are never sufficient to prove the composition of that substance beyond a reasonable doubt.
While positive results from a color-change test conducted in the field may well be sufficient as a preliminary screening mechanism and thus give rise to probable cause, such tests are, by their nature, nonspecific.1 In other words, such tests can indicate only that a substance may contain, for example, cocaine. These tests cannot, and do not purport to, exclude the possibility that a tested substance may be something other than the controlled substance which the test seeks to identify.
Although I concur in the result reached by the majority, I would further hold that the State may never meet its burden to prove guilt beyond a reasonable doubt based solely upon the testimony of a police officer concerning the results of a color-change test conducted in the field.
See, e.g., E Gianelli & E. Imwinkelreid, Scientific Evidence §§ 23 — 2, 23 — 2(B) (1993).