The fingers of a 6-year old girl are too short to reach her own hymen. Masturbation in girls that young, while not unheard of, is usually an indication of sexual abuse or being sexually stimulated somehow.
As far as JR's black Israeli shirt- whenever forensic fiber evidence is considered, fibers are always classified as "consistent with" fibers from something else (i.e a source), as in carpeting, car interior, etc.
This is for the very reason that unless something is the ONLY one in existence,
fibers cannot be said to have come ONLY from that article. However, fiber evidence is often used in criminal cases, and is often the determining factor in guilt, as in fibers from the trunk of a car being found on a body, etc. when it is unlikely that they could have come from any other source. For example- fibers found on a body matching the trunk of a car in which that body was found when the car belongs to someone in possession of the deceased's credit cards, jewelry, clothing, etc. indicates beyond a reasonable doubt that the person knows how that body got in the trunk of their car, even if they were not the actual killer. The fibers in that case indicate that the body was in THAT particular car and not another car of similar make and model.
In this case, you have to consider that it would be very unlikely for any intruder, especially a SFF, to have left fibers consistent with BOTH JR's shirt that he wore THAT DAY (in the panty crotch) AND PR's fleece jacket that she wore THAT DAY (in the garrote knot and tape).
Do we know those fibers were deposited as a direct result of the commission of a crime? Since JB panties were dried in a dryer, and JR's shirt may have been dried in the same dryer fiber from one will deposit on the other. Can we rule out that when PR hugged JB with her red-fiber jacket there was a transfer of red fiber to JB's person, which then transferred to garrote knot and tape?
First, how many individual fibers are we talking about? 1? 20? 300? Second, how "determinative" is fiber analysis? Sure we can say black fibers and red fibers were found, and they are "consistent" with these articles of clothing but they can be consistent with anything? Were any other fibers found, including unidentified? How many fibers were found in the vicinity of JB and/or articles of interest? How do you know that the fibers were not deposited at an earlier point in time, or that JB did not touch these articles of clothing and then transferred them to her panties? Do you know they did not wear that an an earlier time, and transferred to her clothing, and then transferred to those items of clothing? Is it possible LE lied to R's in order to get them to confess as LE did to Susan Smith? :waitasec:
Can we rule out that JR and PR fibers were in the environment where the perp committed the crime, say JB's bedroom and clothing, and then transferred to the perp, then transferred to the said objects?