Guilty by his fibers: suspect confession versus textile fibers reconstructed simulation

Abstract

In one particular criminal case involving murder and theft, the arrested suspect admitted to the theft, but denied responsibility for the murder of the inhabitant of the crime scene. In his confession, the suspect stated that he found the victim's body when he broke into the crime scene to commit theft. For this report, the actual crime scene was reconstructed in accordance with the confession obtained during the interrogation of the suspect, and suspect behavior was simulated in accord to the suspect confession. The number of characteristic fibers retrieved from the simulated crime scene was compared with those of retrieved from the actual crime scene. By comparing the distribution and number of characteristic fibers collected in the simulation experiments and the actual investigation, the reliability of the suspect's confession was evaluated. The characteristic dark yellowish-green woolen fibers of the garment that the suspect wore when he entered the crime scene were selected as the target fiber in the reconstruction. The experimental simulations were conducted four times. The distributed target fibers were retrieved using the same type of adhesive tape and the same protocol by the same police officers who conducted the retrieval of the fibers at the actual crime scene. The fibers were identified both through morphological observation and by color comparisons of their ultaviolet-visible transmittance spectra measured with a microspectrophotometer. The fibers collected with the adhesive tape were counted for each area to compare with those collected in the actual crime scene investigation. The numbers of fibers found at each area of the body, mattress and blankets were compared between the simulated experiments and the actual investigation, and a significant difference was found. In particular, the numbers of fibers found near the victim's head were significantly different. As a result, the suspect's confession was not considered to be reliable, as a stronger contact with the victim was demonstrated by our simulations. During the control trial, traditional forensic traces like DNA or fingerprints were mute regarding the suspect's says. At the opposite, the fiber intelligence was highly significant to explain the suspect's behavior at the crime scene. The fiber results and simulations were presented at the court and the man was subsequently found guilty not only of theft and trespassing but also murder.