 Martz said that environmental conditions would not affect EDTA because it is a stable substance (one evidence sample was outside on the back gate at browns home) and demonstrated this by testing some preserved blood that was over a year old and showed the EDTA level was still the same as his own preserved blood taken only a few days prior.Martz also stated that, although the presumptive test mentioned by Dr. Rieders was positive, the identification test for EDTA was inconclusive, meaning he could not positively identify EDTA was present.Dr.