Here's one reference in the literature about the technique (co-authored by the same guy featured in TFA):
Ehleringer, J.R., Bowen, G.J., Chesson, L.A., West, A.G., Podlesak, D.W., Cerling, T.E. (2008). From the Cover: Hydrogen and oxygen isotope ratios in human hair are related to geography. Proceedings of the National Academy of Sciences, 105(8), 2788-2793. DOI: 10.1073/pnas.0712228105 (geolocation based on oxygen isotopes in hair)
Notice that isotope analysis indicates that a person was or was not in a set of regions at a given time, as in "possibly Texas or Florida." So it's better at narrowing down a list of possibilities than at pinpointing someone's travels. Or as the NOVA story says, it's a "a starting point" for an investigation, not a smoking gun to show off at a trial. (At work, I get to play with some of this stuff, blasting microscopic objects with laser beams and analyzing the atoms that fly off. How fun is that?)