"United States of America v. Kaleil Isaza Tuzman is a rare case involving a chemical method with strong research foundations where the Government argued that the gas chromatography/mass spectrometry (GC/MS) analysis of certain written entries on critical documents produced during litigation was not performed in a reliable manner by the Defendant’s expert. The author of this paper was called as an expert for the Government and a Daubert hearing was granted in the U.S. District Court Southern District of New York. The basis of the challenge focused on the lack of quality control testing; significant deviations from the protocols published in the literature; and the failure to internally validate the method.

The method in question involves the volatile analysis of writing inks to determine if an entry is less than 2 years old. Decades of foundational research has focused on 2-phenoxyethanol (2-PE), a common volatile organic compound used as the principal solvent in many ballpoint inks. In 2002, researchers presented their findings from an extensive study concluding that, “... phenoxyethanol in ink evaporates at a high rate during the first six to eight months following its application on paper ... This process is no longer significant after a period of about two years.”

For ink dating, GC/MS is used to measure differences in the concentration of 2-PE when samples of the questioned ink are heated and unheated, referred to as the solvent loss ratio method (SLRM). Samples of the questioned ink are removed from a document, and then one set is heated at 70°C for 90 minutes and the other set is not, such that the quantity of 2-PE from the heated and unheated samples can be compared. A greater concentration of 2-PE will evaporate from fresh ink compared to older ink. If an ink is ‘fresh’ then it will be much easier to evaporate 2-PE from the samples removed from the ink stroke. If the net difference in the concentration of 2-PE from the unheated and heated ink samples is greater than 25% then the results serve as very strong evidence to conclude that the questioned ink entry is less than two years old. The SLR method has been accepted as an accurate and reliable method by many courts, including Municipal, District, and Federal courts.


The Court concluded that the Defendant’s expert failed to follow the methodology set forth in research papers he testified that he relied upon and the expert did not demonstrate that the modifications to the method were ""subjected to peer review"" or were ""generally accepted"" by the relevant scientific community. The Court also found that the rate of error could not be accurately determined because Defendant’s expert ignored significant quality control protocols designed to mitigate the rate of error. The Court ruled that the Defendant’s proffered testimony was not sufficiently reliable for admission under Federal Rule of Evidence 702 and is properly excluded under Federal Rule of Evidence 403 as more prejudicial than probative."