A recent California case demonstrates why scent lineups continue to be attacked as “junk science” by the defense bar, and why better procedures must be imposed by courts and law enforcement agencies to overcome such criticisms. People v. White, 2009 WL 3111677 (Cal.App. 2Dist. 2009)
The crime occurred on June 7, 2006, in the early evening in Compton, California. Five teenagers were skateboarding when two of them were shot by an assailant. One died. Shell casings were recovered from the crime scene and placed in manila envelopes. Problem one: manila envelopes, as noted by an expert witness for the defense, Lawrence Myers (Auburn University College of Veterinary Medicine), are porous, which allows for the possibility of contamination. Scent pads were later wrapped around the casings for about 10 minutes and the pads were stored in Ziploc bags. Problem two (minor): glass containers would have been better. (See Hudson, D.T., Curran, A.M., and Furton, K.G., The Stability of Collected Human Scent under Various Environmental Conditions. Journal of Forensic Sciences, 2009, vol. 54(6): 1270-1277, noting glass containers were preferable to plastic.) The Ziploc bags were put in an evidence locker for two days. Problem three: The scent samples should have been refrigerated, as noted by the defense expert.
Two officers collected scent from four individuals, including the arms of the defendant, put the scents in boxes and arranged the boxes in a diamond format. Problem four (perhaps minor): If by collecting scent from the arm of the defendant, the court means that it was collected by some means such as rubbing a scent pad along the arm, this would mean that scent was collected from a slightly different body part that the fingers that probably handled the casings collected at the crime scene (while the weapon was being loaded). Some evidence has suggested that scent from different parts of the body may be difficult for a dog to distinguish. (See Brisbin, I.L. and Austad, S.N., Testing the Individual Odour Theory of Canine Olfaction. Animal Behaviour, 1991, vol. 42, 63-69.) Another study contradicted this result, however. (See Schoon, G.A.A., and de Bruin, J.C. The Ability of Dogs to Recognize and Cross-Match Human Odours. Forensic Science International, 1994, vol. 69: 111-118.)
The dog was taken into the middle of the diamond and scented to a pad that had been wrapped around a shell casing. The dog lay down next to the box containing the defendant’s scent. Problem five: There was no discussion of any control trials. European protocols generally call for several control trials to determine if the dog is willing to work on the day of the tests and to verify that the dog is alerting correctly where the “perpetrator” and the target are known to be the same. Also, it may be necessary to determine if the dog has an “attraction” to the scent of a suspect. Problem six: Almost all protocols developed in the Netherlands, Poland, and other law enforcement centers in recent years provide a dog with at least five, and often six or seven choices, sometimes in two lineups simultaneously (See Schoon G.A.A. Scent identification lineups by dogs (Canis familiaris): experimental design and forensic application. Applied Animal Behaviour Science, 1999, vol. 49, 257-267; Schoon G.A.A. A first assessment of the reliability of an improved scent identification line-up. Journal of Forensic Sciences, 1998, vol. 43, 1, 70-75.) In some control lineups, it is often advisable to include “zero trials” where the correct response of the dog is not to alert at all because the item the dog is scented to does not correlate with any of the scents in the lineup.
The handler was unaware of which box contained the scent of the defendant, but while the lineup was being conducted, the two officers who set it up watched from a picnic table 40 to 50 feet away from the diamond formation. Problem seven: No responsible lineup procedure allows the handler to see an experimenter or anyone who knows the location of the target or the suspect’s scent. The “clever Hans” effect can arise even if the handler is blind to the location of the target. This issue was raised by the defense expert (Myers) but dismissed
The defense expert could not interpret the handler’s training logs and could therefore not assess the dog’s reliability. Problem eight: It is the author’s opinion that training logs should always be available to counsel for the defense (or the prosecution in the case of an exonerating scent lineup). The court found this problem was irrelevant because the handler testified as to the dog’s training and was subject to cross-examination. The handler testified that he was not aware that his dog had made any mistakes in 171 criminal lineups. Courts should cease allowing handlers to be the sole means by which major foundational requirements are satisfied in scent lineups. (See the records procedures recommended by the Scientific Working Group on Dog and Orthological Detector Guidelines (SWGDOG), Human Scent Dogs: Scent Identification Lineups (posted at www.swgdog.org). SWGDOG is a forum, with participants from the FBI, other law enforcement agencies, and research facilities involved in canine forensic research.)
The court concluded that the defense expert had done no more than make suggestions for improving the lineup procedure that was used, but that his testimony had not shown the evidence to be unreliable. There was, admittedly, good corroborating evidence here, including the testimony of two eyewitnesses. Part of the case concerned the reliability of visual lineups for eyewitnesses, another area that is not as simple as it once seemed to be. (See, e.g., Wright, D.B. and McDaid, A.T. Comparing System and Estimator Variables Using Data from Real Line-ups. Applied Cognitive Psychology, 1996, vol. 10(1), 75-84.)
Twenty years ago, Professor Andrew Taslitz argued that scent lineups should not be admitted as evidence of guilt in a criminal trial. He noted that research being conducted by Jan de Bruin of the Dutch police might reach a level to be satisfactory for judicial use but noted the research had not yet been published. Adee Schoon, cited in several parentheses above, continued that work and it is this author’s opinion that the scent lineups have reached such a level if conducted with rigorous protocols. Also, some convictions obtained in part by scent lineup results have been overturned, and it is not clear if the public still has a “mythic belief” in the scenting powers of dogs. (Taslitz, A. Does the Cold Nose Know? The Unscientific Myth of the Dog Scent Lineup. Hastings Law Journal,1990, vol 42, 15-134.)
The problem with cases like People v. White is that they risk opening use of a poorly conducted scent lineup to the charge of “junk science.” Almost all of the defects of this lineup would be obvious to the researchers in this area, and most of them could have been easily cured. Some might require that additional dogs be available to confirm the result. Protocols developed in Polish research have demonstrated that requiring at least two dogs—ideally three dogs—to identify the suspect in a scent lineup substantially diminishes the possibility of a misidentification. (Jezierski, T., personal communication, 2010) A proper testing environment and equipment might require additional expense. Nevertheless, in cases where witnesses are fearful or disappear, the scent lineup, if properly conducted at the levels required by the more advanced forensic research centers, may be an appropriate link in the case. Given that the best results that can be expected still allow a small possibility for a false positive (an alert to a defendant who is, in fact, innocent), this evidence should always be limited to cases where there is additional corroboration. That is one strand from the case law of tracking that should be retained in scent lineup cases.