  In 2003, Kuan, Charnley, and co-workers reported the detection of
interstellar glycine (NH2CH2COOH) based on observations of 27 lines in 19
different spectral bands in one or more of the sources Sgr B2(N-LMH), Orion KL,
and W51 e1/e2. They supported their detection report with rotational
temperature diagrams for all three sources. In this paper, we present essential
criteria which can be used in a straightforward analysis technique to confirm
the identity of an interstellar asymmetric rotor such as glycine. We use new
laboratory measurements of glycine as a basis for applying this analysis
technique, both to our previously unpublished 12 m telescope data and to the
previously published SEST data of Nummelin and colleagues. We conclude that key
lines necessary for an interstellar glycine identification have not yet been
found. We identify some common molecular candidates that should be examined
further as more likely carriers of several of the lines reported as glycine.
Finally, we illustrate that a rotational temperature diagram used without the
support of correct spectroscopic assignments is not a reliable tool for the
identification of interstellar molecules.
