It is indirect circumstantial evidence and it has been very reasonably explained. The fibers by reasonable doubt as to the matchup, and that fibers easily could have come from other sources. The fiber is also explained -- if they demonstrated to match beyond a reasonable doubt, which they have not -- by direct or secondary contact between Brenda and Westerfield on the dance floor, or by ANY of the visits of Brenda and Danielle to the house, or by an entirely reasonably plausible sneak visit of Danielle into the motorhome in any of the many months more than a year it was available to neighborhood kids to do so. The last also explains the DNA-bearing spots, or those could be explained by deliberate -- and felonious -- evidence contamination.
The many irregularities in police procedure give some reasonable credence to the felonious police work possibility, but even that possibility is not necessary to reasonably explain the DNA spots and the hair.
Further the exceptional agreement of the bug experts in determining the most likely date the body was dropped -- when Westerfield was under a high degree of police scrutiny. Ignoring that -- as to reasonable doubt -- is an egregious violation of a juror's sworn duty