Key Concepts

  • A properly qualified expert can examine the microscopic characteristics of fibers (such as a fiber found on defendant’s shoes and a fiber from the carpet in victim’s home) and render an opinion about whether those fibers match.
  • Expert testimony on fiber analysis has been admissible for many years. North Carolina’s appellate courts have not yet reconsidered the issue under Daubert, or in light of recent criticisms of the science behind the field, but federal courts applying Daubert have allowed it into evidence.

Overview and Technique 

The North Carolina State Crime Lab Trace Evidence Unit can analyze and give expert testimony about fiber evidence such as string, yarn, fabric, tape, and cordage. The analyst will microscopically examine and compare variables such as “the amount of dye absorbed, the amount, particle size and distribution of delustriant (soil-hiding chemicals), the shape of the fiber (which could be round, star-shaped, triangular, multi-lobed, etc.), color, detail (such as striations on the fiber), light-polarizing characteristics and solubility characteristics.” State v. Head, 79 N.C. App. 1 (1986)

Based on that comparison, expert testimony may be offered to show that certain fibers do or do not “match,” typically for the purpose of helping to prove or disprove that the suspect had contact with a particular person or place. See, e.g., State v. Vestal, 278 N.C. 561 (1971) (no error to allow an expert in the field of analyzing and comparing fibers to testify “concerning the similarity of the drapes found in the defendant's warehouse with that found upon the body”).  

Practice Pointer

What does a “match” mean? 
The prosecutor should talk to the witness before trial and clarify how the witness will (or will not) be able to express the certainty of the results. For example, the witness may be able to testify that the fibers have “matching characteristics,” they are “consistent with each other,” or even that they are the “same material,” but may or may not be able to state that this means the two fibers definitely came from the same source. See, e.g., State v. Head, 79 N.C. App. 1 (1986) (“expert in fiber identification and analysis... testified that when he said one fiber was “consistent with” another, that meant that there were no inconsistencies in any of the details examined”); State v. Coble, 20 N.C. App. 575 (1974) (SBI expert analyzed fibers “by microscopic examination and chemical testing of the dyes” and opined that “the fibers in State's Exhibit 5 were the same material as the fibers in State's Exhibit 6”). 

Admissibility and Reliability 

North Carolina trial courts have found expert testimony regarding fiber analysis to be reliable and admissible in evidence for many years. See, e.g., State v. Payne, 328 N.C. 377 (1991) (fiber expert testified that red fiber from defendant’s shirt was microscopically consistent with fiber from rug in victim’s home, and microscopically inconsistent with fiber taken from the carpet in defendant’s own residence – the fact that the test sample was taken from defendant’s home 49 days after the murder only went to weight, not admissibility, since it’s common knowledge that people don’t frequently change their carpets); State v. McDonald, 312 N.C. 264 (1984) (“State showed a sufficient chain of custody to permit the admission into evidence of the red emergency room bag, the pants, the coat and the results of the fiber analyses performed on them”); State v. Woods, 286 N.C. 612 (1975) (expert opinion of similarity of fibers from victim’s dress compared to those found in defendant’s vehicle ruled proper in murder, rape and kidnapping prosecution: fibers were reasonably rare and it was unlikely that the fibers came from a source other than the dress of the victim); State v. Mandina, 91 N.C. App. 686 (1988) (expert testified that “some of the fibers taken from the trunk carpet and rear floor mat of the vehicle were consistent with fibers taken from a burglarized home and that other fibers matched those taken from hallway carpet at the motel where defendant allegedly stayed”). 

Like many other forensic evidence disciplines, fiber analysis has recently faced criticism over the need to conduct more objective and systematic testing to evaluate its validity, and to quantify the significance of declaring a “match” between two fibers. See Modern Scientific Evidence: The Law and Science of Expert Testimony 114, David L. Faigman, et al. (2016-17 ed.) 

There do not yet appear to be any post-2011 North Carolina appellate cases analyzing the reliability and admissibility of this type of evidence under the amended version of Rule 702 that adopted the Daubert standard. However, several federal courts have considered the admissibility of fiber analysis under Daubert and allowed this type of expert testimony into evidence. See U.S. v. Youngberg, 43 M.J. 379 (C.A.A.F. 1995) (applying Daubert and holding expert’s testimony that “fibers taken from the victim's body and car matched fibers from appellant's t-shirt” was properly admitted, and noting that “fiber-analysis evidence has been routinely admitted in criminal cases both in Federal and state criminal courts for many years”); see also U.S. v. Barnes, 481 Fed. Appx. 505 (11th Cir. 2012) (unpublished) (finding that testimony of FBI trace evidence expert in “hair and fiber analysis” regarding microscopic analysis of fake beard hairs satisfied the “flexible nature of the Daubert inquiry” and did not overstate the certainty level of her findings); U.S. v. Lujan, 2011 WL 13210238, No. CR 05-0924 RB. (D. New Mex. 2011) (unpublished) (denying motion to exclude fiber analysis expert’s testimony comparing fibers on shoes to fibers from a blanket – trial court found that the basis for expert’s opinion was reliable, relevant, and admissible under Daubert).

Portions of this entry were excerpted from the North Carolina Superior Court Judges’ Benchbook, “Criminal Evidence: Expert Testimony,” Aug. 2017, Jessica Smith.