Manhunter analysis - part 4: Problems with the FBI's hair analysis

CATEGORY: MOVIES     [Hidden plot related]

The toilet tissue note found in Lecktor's cell. Note that it is in two pieces.


In this and the next post, we are going to go over some things which suggest that the FBI investigators should not have been as certain as they were, that the entire note found in Lecktor's cell was actually written by the "Tooth Fairy" (Francis Dollarhyde). These things involve the incorrect use of lab results, the failure to carefully look over key pieces of evidence, and some other related phenomena.

Let us first look at the hair sample results. Recall that when a note (written on toilet tissue, supposedly in its entirety by the Tooth Fairy) is found in Lecktor's cell and is brought to the FBI lab in Washington, there are also some hair samples brought along with it. The lab technician discovers a single one-half inch hair on the note, and she is to compare it to hair samples from Lecktor's comb, whisker samples from the electric razor the prison staff allows him to use, and hair from the guard who removed the note from his cell.

In the group discussion after the lab analyses have been completed, the lab technician (Beverly Katz, shown at left) who analyzed the hair confidently states that the scale counts and core size of the hair match the blond hair found in the Jacobi's residence. Therefore, her conclusion, which she firmly states, is that the note was written by the Tooth Fairy. However, a little research shows that the lab technician was in error when, based on the reason she gave (the matches with scale counts and core size), she concluded that the two hairs must have come from the same person.


The quoted material below is taken from the FBI standard, the Encyclopedia of Security Management, 'Hairs and Fibers' section:

"Hairs. Examination of hair can determine if it is animal or human; if animal, the species from which it originated (dog, cat, deer, etc.), and if human, the race, body area, how removed from the body, damage, and alteration (bleaching or dyeing).

The finding from a hair examination is good circumstantial evidence, but not positive evidence. An examination can conclude whether or not a hair could have originated from a particular person based on microscopic characteristics present in the hair. Age cannot be determined, but gender may be determined depending on the condition of the hair's root."[a] (emphasis not in original).

Scale counts and core size are microscopic characteristics of hair. Therefore, the lab technician was in error when she stated that the hair must have come from the Tooth Fairy.

In the next part of the analysis, we will go over a key item which some of the investigators, including Graham and Crawford, overlooked.


a. Fay, John. Encyclopedia of Security Management. Butterworth-Heinemann, 2007. Google Books, pp. 186-187. URL = https://books.google.com.