Deputy and Court Officer — #2, 2011
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How to Prevent Cueing Arguments from Getting Canine Evidence Thrown Out in Court
John J. Ensminger and L.E. Papet


Drug, bomb, accelerant and other detection dogs are alert to specific chemicals during investigations and thereby produce evidence used in a wide variety of criminal prosecutions. At trial, defendants may attack the admission of such alerts, possibly presenting evidence a dog was not trained, tested or certified according to standards of states or professional organizations. Arguments may also be made that a dog has a record of false alerts and is not reliable. A handler may claim some apparently false alerts were really the dog’s detection of a residual odor, i.e., an odor of an item previously but no longer present at the location. One Maryland court accepted evidence that a dog could alert 72 hours after drugs were no longer present.

While the presence of confirmed residual odor does not constitute a false alert, other unexplained alerts may be false. In an extreme case, a handler may call an alert when in fact none took place because of a hunch that contraband will be found even if the dog does not smell it. Also, a handler may intentionally cause an alert using a gesture or word he knows will induce the dog to perform its alerting behavior. See Figures 1 and 2. Even without this kind of inappropriate action, a handler’s belief that contraband is present may influence the dog to alert through a phenomenon known to scientists as the “clever Hans” effect, from a horse once thought to be able to How to Prevent Cueing Arguments from Getting Canine Evidence Thrown Out in Court By John J. Ensminger and L.E. Papet* solve arithmetical questions. Either intentionally or unintentionally causing a detection dog to alert is referred to as cueing.

A record of false alerts during negative controls may obviate a residual odor argument (Jennings v. Joshua Independent School District). In a recent Florida Supreme Court case, Harris v. State, the court described cueing as a type of handler error and held that “any presumption of reliability based only on the fact that the dog has been trained and certified does not take into account the potential for false alerts, the potential for handler error, and the possibility of alerts to residual odors.” the court held that field records were essential in determining the reliability of the dog.

Courts have often rejected cueing defenses when a battle of the experts does not clearly resolve the issue (see U.S. v. Ludwig). In U.S. v. Clarkson, however, a motion to suppress was granted because the court credited the defense expert above the prosecution’s expert. Part of the testimony of the defense expert was that the handler “likely cued” the dog “by considerably slowing his search pattern when he approached the passenger side door and standing in a manner so as to block the dog.”

Observations of multiple canine teams in different training sessions and venues reveal a wide variety of situations in which a handler may actually cue a dog, including:
- A change in the handler’s voice – pitch, speed, volume – sometimes appears to elicit a response; talking to the dog so much during a sweep that the dog appears to alert from frustration.
- Praising prematurely or encouraging the dog too much during a sweep may induce an alert.

Movements may signal a dog, including crowding (Figure 2, slide 2), changing pace, walking backwards in front of the dog while tapping surfaces for the dog to sniff (Figure 1, slide 1), stopping in front of or beside the dog, repeatedly searching the same area, staring at a place where an item may be hidden, increasing tension on the leash (Figure 1, slide 2), making various hand movements, such as pointing to a location or vicinity of the suspected target odor or reaching for a reward prior to the dog’s final alert (Figure 2, slide 3).

A recent study is likely to increase the number of claims of cueing in criminal trials. In the study, “Handler Beliefs Affect Scent Detection Dog Outcomes,” published in the May 2011 issue of Animal Cognition, researchers at the University of California at Davis determined that 17 of 18 police dogs, when walking through a series of rooms in a church, alerted to the presence of drugs or explosives though no contraband items were in the rooms at the time. The handlers had been led to believe that drugs or explosives would be present and marijuana and gunpowder were briefly placed in the rooms before testing began each day. The research may have been flawed by the possible presence of residual scent, as well as by first aid kits and art supplies in church rooms, which may contain target scents. Dogs may also have cued each other by leaving saliva at some locations.

What Law Enforcement Must Do
To deal with this changing judicial landscape, law enforcement administrators should take a number of steps. First, it is important for handlers to recognize that cueing is a potential problem for any handler and that they must constantly review their procedures to recognize when they may be responsible for a dog’s alert. Handlers should keep complete records, documenting each alert separately, both in training and in the field, and recording to the extent possible why each alert happened. Was a target located? If not, could the past presence of a target be documented? How long prior to the sniff was the target present?

The handler should understand how effective the dog is at recognizing residual odor. Is other material present that may contain a target odor? In training, these issues can be controlled, but in the field it may often be impossible to verify whether a target was in previously in a location. Handlers and trainers should assure that negative controls are regularly introduced into training and testing trials. Canine teams that regularly alert despite the absence of target odors should be reviewed for cueing and other possible problems or errors.

Dogs should work as independently as possible during a sweep, without distractions such as talking, movements, evident impatience, or anxiety. Considerable progress in reducing cueing and other handler errors can be made by having training sessions observed by experienced trainers and handlers. Videotapes should be made where possible, so that handlers can be shown where they might be cueing. Dashboard camera videos can also be reviewed to see if cueing may be occurring in the field. Certainly defense attorneys will ask their experts to review dashboard camera videos for indications of cueing (SouthDakota v. Lockstedt).

Police supervisors should be sure that handlers, whether inside departments or retained as contractors, regularly participate in continuing education, with dogs periodically evaluated for possible cueing and other problems or errors. With such preparations, supervisors will not feel blindsided by cueing allegations on matters that reach trial, but will be able to provide evidence supporting the handler’s skill and the results of the deployment of a dog.

Major Vince Hester of the Cobb County Sheriff ’s Office in Georgia said: “Law enforcement handlers are under increasing attack in court due in large part to expert claims of cueing. It is such an important issue that I have added an entire section of training to address various forms of cueing. I’ve got a 95% plus confiscation rate on federal search warrants, so I can stand toe to toe with any defense lawyer.”

Police and sheriff s’ offices can protect the integrity of their canine units and provide valuable evidence for prosecutors but they must anticipate cueing defenses by taking appropriate precautions in training, testing, and recordkeeping.
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