Friday, April 10, 2009

A "scent lineup"? Rover in the witness box

Erroneous eyewitness testimony and the makeup of lineups and photo arrays have been the subject of much discussion this spring as key contributors to false convictions, which makes me wonder how high the error rate might be for a "scent lineup," particularly when the witness in question is a dog?

To say the least, that would make cross-examination more difficult.

At the Texas prosecutors' user forum, we find a discussion of "scent lineups", including case law on their legality, begun by a commenter from Bryan:
My department is researching "police" bloodhounds, specifically the use of scent evidence lineups in criminal cases. If anyone knows where I can find case law and/or citations on this topic it would be greatly appreciated. Personal opinions on this topic are welcome too.
An ADA from Parker County chimed in with some personal background:
As an intern in the Fort Bend County DA's office, i got to write the appellate brief on Marcus Omar Winston v. State. 78 S.W. 3d 522. At the time, Texas had very little case law about scent hounds that were not drug dogs and as such, much of my research involved out of state case law. The Houston Court published the opinion and its holding is still good law.
Discussion on the string centered around Deputy Keith Pikett out of the Bend County Sheriffs Office. I'd not heard of Mr. Pikett's dogs, but a quick Google found they've earned some measure of regional renown.

They've also drawn litigation from those who question whether it's Pikett or the dogs doing the leading. A judge in January refused to dismiss Pikett from civil litigation that alleges he led his dogs to a suspect in Victoria by re-scenting them near a location targeted by local police. The lawsuit accuses Pikett and the Victoria PD of using "contrived and unreliable methods ... to create evidence" in a murder case.

Looking around for scientific evaluations of dog-scent evidence, I didn't find much. Here's a description of a "scent lineup" involving Pikett's dogs from the Austin Statesman a couple of years ago (5/15/07):

A police officer went to [defendant Reginal] James’ jail cell and lightly touched his skin with a gauze pad. Then Hawthorne called Pikett and told him he needed to see him soon.

The detective took the sample from James in a Ziploc bag and started the three-hour drive to meet with Pikett. He also took four other gauze pads that had been wiped on the woman’s bed, her ring, her dresser and a doorway.

In the lineup, the dogs’ job was to see if the samples from the crime scene matched the sample from James.

The lineup consisted of six cans about 10 feet apart — one had a sample from James, and five contained gauze with the scents of people unrelated to the case.

The dogs were then given the scent from one of the crime scene samples and went to the cans to see if there was a match. The process was repeated for each sample from the crime scene.

Both dogs — Quincy and James Bond — matched James’ scent to the crime scene in all four tests.

What little research-based analysis I could find online did not support dog-scent evidence having a scientific basis, though Texas courts appear to allow it. This paper from 1999 concluded that:
Canine identification of human scent does not yet have a proper scientific foundation ... however, such expertise should not be called junk science" in general.

The method has been introduced into trial proceedings too early, by overly hasty police practitioners which have caused miscarriages of justice. Moreover, there have been no field studies. ... In this situation the criteria of "scientific evidence" like those in Daubert, are of great importance. ... After all, nobody should be convicted solely on the basis of a dog wagging its tail.
Interesting stuff - I'd never heard of "scent lineup" before and wonder what is the real-world error rate and to what extent the technique would hold up to scientific scrutiny?

RELATED: From Fortune Magazine, "Sit, Stay, Testify!"

MORE: In the comments, a reader suggests looking at the Wikipedia entry for "Clever Hans," and indeed it appears to be on point. The entry begins:

Clever Hans (in German, der Kluge Hans) was a horse that was claimed to have been able to perform arithmetic and other intellectual tasks.

After formal investigation in 1907, psychologist Oskar Pfungst demonstrated that the horse was not actually performing these mental tasks, but was watching the reaction of his human observers. Pfungst discovered this artifact in the research methodology, wherein the horse was responding directly to involuntary cues in the body language of the human trainer, who had the faculties to solve each problem. The trainer was entirely unaware that he was providing such cues.[1]

In honour of Pfungst's study, the anomalous artifact has since been referred to as the Clever Hans effect and has continued to be important knowledge in the observer-expectancy effect and later studies in animal cognition.

For these reasons, blind administration would be critical for "scent lineups" to be valid. If the dog handler knows ahead of time which choice contains the scent of the suspect, it would be easy for dogs to pick up on nonverbal cues - like Clever Hans did with his trainer - instead of reacting solely to a similar scent. And since the dog can't be cross examined, no one can know why the animal made the choices it did. This is poor evidence, particularly if used without blind administration.


Roy said...

This is scary. Check Wikipedia for "Clever Hans". What we have here is not a dog bearing witness but a trainer having a dog do tricks.

TxBluesMan said...

The lead case on bloodhounds in Texas is Parker v. State, 80 S.W. 1008 (Tex. Crim. App. 1904), rev'd on other grounds, which stated that bloodhound tracking was admissible:

"when it is shown that the dog is of pure blood and of a stock characterized by acuteness of scent and power of discrimination, it must also be established that the dog in question is possessed of these qualities, and has been trained or tested in their exercise in the tracking of human beings, and that these facts must appear from the testimony of some person who has personal knowledge thereof." Parker, at 1011.

Other cases on bloodhounds in Texas are:

Risher v. State, 227 S.W.3d 133 (Tex. App. Houston, 2006) - scent line up

Martinez v. State, 2006 Tex. App. LEXIS 10758 (Tex. App. Houston, 2006) - scent line up

Robinson v. State, 2006 Tex. App. LEXIS 10220 (Tex. App. Beaumont, 2006) - scent line up

Winston v. State, 78 S.W.3d 522 (Tex. App. Houston, 2002) - scent line up, cited in main post

Briseno v. Cockrell, 274 F.3d 204 (5th Cir., 2001) - tracking

United States v. Watkins, 741 F.2d 692 (5th Cir., 1984) - tracking specific individual

Until someone comes up with a basis for suppressing bloodhound evidence, it is likely to be admissible.

Rage Judicata said...


Here's a quote from the Supreme Court:

"A black man has no rights a white man is bound to respect."

Precedent isn't everything. As far as expert/scientific evidence goes, it has to be shown to be reliable once challenged.
So case law wouldn't mean as much in a courtroom where evidence is scrutinized, but in the clown courts we call criminal courtrooms, I'm sure a 1904 scientific ruling saying a dog mus be pure blood is enough.

Anonymous said...

I remember this one from Professor John Kaplan's Exidence casebook:

The case is Buck v. State (Oklahoma Court of Criminal Appeals, 1943). I sometimes think that Professor Kaplan included it just because the opinion was written by a Judge whose last name was Barefoot.

Paul-United Kingdom said...

Sheee!!! My jaw dropped when I seen this one! The East German secret police (The STASI) used to do this! They would collect samples of dissidents and store them in bottles and maintain sniffer dogs which could be used for identification of suspects. If you want to see how it is done watch the movie "The Lives of Others" One of the scenes is where the secret policeman removes the chair cover after interogatting a suspect and placing it into the jar. I have also visited the STASI headquarters in Berlin which is now a museum and seen the bottles.

TxBluesMan said...


If you note that most of the cases listed were in the last 10 years, you might have a better shot at convincing someone, rather than babbling on about 'clown courts.'

You should remember that in Texas, the Daubert test Daubert v. Merrell Dow Pharm., 509 U.S. 579 (1993) only applies to the hard sciences and for outside the hard sciences, the Nenno test applies, from Nenno v. State, 970 S.W.2d 549 (Tex. Crim. App. 1998). (Daubert is sometimes referred to as Kelly in Texas, from the case that applied the Daubert test in Texas).

In the cases I cited from Texas, the scent line-up passed the Nenno test, so you would either have to get that case overturned by the CCA or get a Federal Court to change it.

Otherwise, all that they have to show is "(1) the qualifications of the particular trainer, (2) the qualifications of the particular dog, and (3) the objectivity of the particular lineup." Winston, at 527.

You might try actually reading the opinions - the evidence was challenged...and admitted.

Anon 11:31,

While similar, an Oklahoma case doesn't have precedential value in Texas. It is neat that Barefoot cited Parker in his opinion though...

Roy said...

When using bloodhounds to follow a specific scent, the dogs are all leashed together so that they don't run off following different 'identical' scents, and when they do have divergent opinions, the handler decides which way the dogs want to go. Also, when a dog loses a scent trail, it may take off on the smell of crushed grass, so that the scent of a running escapee turns into a little girl on her bicycle -- in which case the cops would eventually admit that everybody makes mistakes. Their attitude is that they are always right unless they are proved ridiculously wrong, in which case, it's always excused as 'an honest mistake'.

TxBluesMan said...


That is actually not the way that they use bloodhounds to track, although it does look good in the movies.

You may also want to look at the only scientific study that I've found that has been peer-reviewed (Harvey, LM & Harvey, JW; Reliability of Bloodhounds in Criminal Investigations, J. Forensic Science, 40:811-816, 2003. In that study they found that properly trained, veteran bloodhounds completed a good track 96% of the time on a 48 hour old track, with no false positives. Trails that were laid included a college campus and a park with over 1,000 uninvolved people in it between the time the trail was laid and the track.

Note that this is only good for bloodhounds - the use of other dogs to track has not been tested for reliability, nor has non-bloodhound scent lineup evidence been admitted into evidence that I can determine.

Anonymous said...

Roy you been watching to much TV.


Gritsforbreakfast said...

Yes, Bluesy, we're all aware that the Texas Court of Criminal Appeals will approve any hare-brained "expert" if it will help execute a death row inmate like Nenno. Such issues shouldn't be decided on death penalty cases, IMO, because the current CCA is so proactively focused on maximizing their execution numbers - an example of bad facts leading to bad law. When the GOP is no longer in power on that court here in a few years, I've little doubt that Nenno will be one of the early cases that's overturned by a court more concerned with justice than maximizing their number of scalps.

BTW, your bloodhound study doesn't speak to the question of scent lineups, and a 4% error rate is pretty high - particularly if you happen to wind up in that 4%. The article was right that dog sniffs don't even deserve the term "junk science." They're not science at all, just a dog's educated guess.

Scent lineups COULD be scientifically tested - the fact that they have not been is arguably quite telling. Nobody wants to establish an error rate they'd have to cop to later in court. Perhaps it's not junk science, but it's certainly junk testimony.

TxBluesMan said...


You did notice, I hope, that there were 0% false positives?

In other words, when an error was made (in only 4 out of 100 instances), it was in favor of the suspect?

Once again, you are in favor of eliminating tools for law enforcement and the prosecutors, so that the guilty can walk.

Why do you have such a bias against the police and prosecutors?

Anonymous said...

Paul, thank you so much for the information on how the Stasi operated. As you can tell from Texas BluesMan's comments, the people in Texas are curently suffering under a police force that is quite similar to the Stasi. They don't question, and they are believers. They are arrogant and believe they are better than others. You see, anything that enforces their authority must be correct.

Please do your best there in the UK to spread the news of our Texas "justice" system.

It's horrible. I believe a lot of it's unconstitutional, but it's been able to operate under the national US radar because they've set up many duplicate courts systems and fake hearings to give the impression they are following national standards.

In a situation like this, scorn and ridicule can only help, especially on the international stage.

Anonymous said...

In the post above, when i said "they" I meant the police force

Unknown said...

all that they have to show is "(1) the qualifications of the particular trainer, (2) the qualifications of the particular dog, and (3) the objectivity of the particular lineup." Winston, at 527.

I don't know about the law but I do know about dogs. There is no way to tell what a dog "smells". It is like scientifically "proving" the existence of God. There is no way that a smell lineup should ever be admitted into any kind of evidence. And a bloodhound can't smell any better than your sister's toy poodle. He just has a different outlook on life.

Gritsforbreakfast said...

Bluesy, you keep ignoring that the study you cited isn't remotely on point to the subject of the blog post. The answer to "why" I would deny the tool to law enforcement (or rather, why I think it should be excluded from the courtroom) is that there's no scientific evidence a "scent lineup" is reliable and the dog can't be cross examined. A more apropos question is why do you support using untested junk testimony by a dog in the courtroom?

If this is a legitimate technique, it will stand up to testing. If not, it would be debunked by a thorough scientific review. Either way, those seeking truth instead of just convictions have nothing to lose by insisting that methods used in court are verifiable, reliable, and scientifically valid.

TxBluesMan said...


First, as I noted in my earlier posts, it is not a hard science and in Texas that means that it has to pass the Nenno test, not the Daubert/Kelly test.

I also notice that you failed to address the fact that there were no false positives in the study on tracking. There is no reason to believe that it would be different on a scent line-up study.

Do you object to Nenno's execution for the murder and rape of a 7 year-old? That he confessed to? Told the authorities where the body was hidden in his attic? That he repeatedly violated the girls dead body?

The testimony that Nenno objected to was from Kenneth Lanning and was in the punishment phase of the trial. Lanning had studied the sexual victimization of children for 23 years, had 25 years with the FBI, 15 of which were in the Behavioral Science Unit. Nenno objected to Lanning's testimony since there were no data on the 'future dangerousness' of sex offenders and the area had no empirical testing.

The court, probably realizing that to get that data and empirical testing you would have to accept the deaths of third party innocent parties, distinguished between the hard and soft sciences.

If you overturn the Nenno test, you put killers like him back on the street.

I don't believe that is acceptable.

Gritsforbreakfast said...

Bluesy, you're just trolling now. Why don't you go put this crap on your own blog for a change?

Your comment about Nenno is just stupid obfuscation. You know full well I was critiquing the test for evidence in the case, not his conviction. That's purely disingenuous - a typical sign of a weak argument.

And I didn't address your claim about no false positives because the study itself (as I DID point out) is simply not on point to the question at hand. Find a peer reviewed study that supports "scent lineups" and I'll debate the specifics with you, but I see no need to react to every red herring you throw out.

If someone is guilty, it should be provable using legitimate evidence, not untested pseudo-science. If scent lineups are valid, they will withstand scientific scrutiny. If they're not, you're arguing for a position that encourages conviction of innocent people based on junk evidence.

Cherry said...

Hey Bluesy - as far as Nenno's conviction goes - if this evidence was in the punishment phase, then overturning it would result in a new punishment hearing. It would not mean putting him "back on the streets" but the possibility of a life sentence instead of a death one. Turn down the hype a little, please.

A in Texas said...

As an owner of a true bred bloodhound and a fan of concept of using animals to aid in Law Enforcment, I have one thing to say about scent lineups: Bullshit.

You can train your dog to track the faintest scent of a convict halfway across the county, but that won't stop him from being distracted by the scent of BBQ sauce or of fresh rabbit tracks. A dog will behave like a dog, no matter how disciplined.

Can you use them to point you in the right direction? Sure. Can you arrest someone based on the reaction of a Dog? NO. That's why drugs dogs searches alone are inadequate for charges.

Paul-UK said...

I found this clip on Youtube from the opening scene from the "Lives of Others" Yes I know it is subtitled but Grits if you see this, you may also want to consider it not only from collecting samples for dogs to identify suspects, but also how presumptions of guilt can lead to the authorities dismissing perfecttly good alabis as addmission of guilt. (By the way, it is a really good film, everyone should see it!)

TxBluesMan said...


Well, then try looking at:

Harvey et al, The Use of Bloodhounds in Determining the Impact of Genetics and the Environment on the Expression of Human Odortype, Journal of Forensic Sciences, Vol. 51, Issue 5, pp. 1109-1114, 2006.

Curran et al, Analysis of the Uniqueness and Persistence of Human Scent, Forensic Science Communications, Vol. 7, No. 2, April 2005.

Tomaszewski et al, Scent Identification Evidence in Jurisdiction, Forensic Science International, Vol. 162, pp. 191-195, 2006.

The uniqueness of individual human scent was shown in:

Curran et al, The Frequency of Occurrence and Discriminatory Power of Compounds found in Human Scent across a Population determined by SPME-GC/MS, Journal of Chromatography B, Vol. 846, Iss. 1-2, pp. 86-97, 2007.

The reason I commented on your blog is because you posted on the subject, falsely claiming it as 'junk science' or 'junk testimony,' citing a paper from 10 years ago while it is clear that additional research has been done on the subject of scent identification.

If you don't want opinions that conflict with yours, say so. You have plenty of people here that are more that happy to agree with you, to merrily go along with whatever position you take.

Gritsforbreakfast said...

Bluesy, I didn't ask for general references on human scent. If there is research supporting the validity of scent lineups as described in the post, please point to it. If not, I'm done with you.

TxBluesMan said...


Did you even read the studies, or just the abstracts?

The first one referenced, (Harvey 2006) determined that bloodhounds could accurately distinguish between identical twins that lived together, identical twins that lived apart, and non-related pairs, and related pairs. Environmental conditions were strictly controlled (test subjects had to use the same soap, shampoo, etc for about 1 month prior to the test), DNA testing was conducted to compare genetic markers, and the testing was done in a double blind manner to prevent the handler from being able to influence the hound. The study concluded that: "Our research would suggest that bloodhounds can identify a person by their individual odor..."

That is exactly on point for scent lineup.

Even more specific is the study by G.A.A. Schoon, The Effect of Aging of Crime Scene Objects on the Results of Scent Identification Line-Ups using Trained Dogs, Forensic Science International, Vol. 147, pp. 43-47. The study found:

"The results show that whilst the dogs perform faultlessly in matching odours collected on the same day, the results drop to a lower level and become more variable in the period studied (2 weeks to 6 months)."

This was a study done on the exact subject of your post - scent line ups, using a blind method of conducting the test.

Again, if you don't want to hear the truth, tell me and I'll go away - but you have plenty of scientific studies completed after the dated study you cited that show that the field is a valid one.

I hope that you are open enough to see the facts, and not blinded by your bias and apparent dislike of being contradicted.

oushin said...

The fact that the dog disguishes between identical twins proves that bloodhounds do not identifiy people by any scent that is native to a person's core being.

Identical twins are genetic clones. Any dog distinguishing them by scent isn't distinguishing the human scent of the individual because identical twins are not biological individuals.

The dog must necessarily be distinguishng some other scent differences on these clones perhaps the odor of the food they ate, the smell of their clothes or the smell of their friends, or who knows what environmental variable that came into play before the commencement of the sniffing. The bloodhound can't testify to explain what he smells or how he made this determination.