Results indicated that ninhydrin produced relatively uniform visible absorption spectra when reacted with the nine chosen amino acids. Only one amino acid, lysine produced a significant variation and this might have been due to additional reactions taking place with the amino group on the side-chain of the molecule. DFO also produced relatively uniform results with respect to both visible absorption spectra and luminescence spectra, regardless of the amino acid. A completely different situation was observed with indanedione; with formulation and development condition typically employed in casework, the spectra recorded from the developed amino acid spots suggest an incomplete reaction or the formation of by-products due to non-ideal reaction conditions. Indanedione-zinc produced remarkably consistent visible absorption and luminescence spectra, regardless of the amino acid tested. References, tables, and figures