that. >> to find out, scientists looked for evidence in her hair. >> it turns out that the hair and in some cases toenails or fingernails are good indicators of body loads of certain elements. in particular, in the case of arsenic, it's often used as hair where it's concentrated in the hair. >> since hair grows approximately one-half inch per month and leita's hair was three inches long, this gave scientists a six-month time line to see when leita was poisoned. each half inch piece of hair was tested with neutron activation analysis. >> neutron activation has some advantages and one is that it is considered to be nondestructive. that is, solid samples can be irradiated directly without having to dissolve the sample in any way. >> the results were surprising. leita ingested a massive dose of