Introduction to V.O.C.s K9 Olfaction and Forensics

 

ASCT Instructor

Carroll College Anthrozoology Instructor ( Ret.)

 

Remember the old example used for decades in K9 on what a dog perceives scent wise? You walk into a hamburger joint and you smell burgers. The dog smells burgers, cheese, pickles,and a sesame seed bun. Think V.O.C.s.....

The chemical compounds that we are most concerned with in K9 namely narcotics, explosives, and personal scents are just that. Compounds. They are composed of a number of different chemicals of varying molecular weights, which when joined together in consistent ratios to one another comprise the odors we train on and for.

Volatile Organic Compounds are those component parts of the odors. To be considered Volatile a chemical will ,very generally speaking,have a molecular weight of 200 or under. This all basically means the molecules are fast moving and easily agitated by applying the old principles of heat and pressure thus making them easily available to the K9s olfactory ability. As we know, many narcotics are in the range of MW ( Molecular Weight) 350 and our dogs have no problem accessing them. One reason for this is that the narcotic compounds are in turn comprised of various V.O.C.s which when presented to K9 olfaction in their consistent ratios will spell out a message to the brain...” Heroin”. As we shall see if the ratios are inconsistent as in the case of something coming close to a mimic of the odor, it will spell out a message to the brain of the K9 “ nothing of importance”.

If you have taken Dr. Aycock's course on Neuroscience particularly dealing with K9 Olfaction it delves deep into the subject of why and how this happens. I will attempt to distill it down as succinctly as possible. Think of the 26 letters in our alphabet. They are responsible for spelling a virtually infinite number of words. Think of the 1,000 genes in the K9 genome that are responsible for olfaction....if each one only identified one odor the number of combinations possible staggers the mind. When an odorant ( airborne molecule) is detected by an OSN ( Olfactory Sensory Neuron ) and yet another odorant from the compound is detected by another OSN they can be paired together to create the dog's perception of those two compounds together- the very definition of 'odor'..at least in our business. The same is true for compounds with a great many more components than just two. Just as words in the alphabet have letters as their component parts, odors have V.O.C.s as their component parts and together they spell things out to the dogs.

NARCOTICS

The Volatile Organic Compounds that comprise the various narcotics, like other compounds can be broken down and identified by a process called Solid Phase Micro Extraction ( SPME) and even printed out in a graph ( Gas Chromatography GC )which easily shows the amounts and ratios of each VOC to one another. ( Remember ratios are important...) ( Curran et al., 2005 )We need not dissect this process for the purpose of this article but suffice it to say it is a handy way to identify the predominant V.O.C.s in a given compound and more importantly, the most common denominators in similar compounds. i.e. the various types of Heroin and Cocaine. SPME-GC analysis has even made it possible in many instances to identify the region and/or even the cartel a given sample of heroin or cocaine came from due to differences in manufacture and use of certain chemicals and solvents by the various manufacturers.A forensic advantage.

Bear in mind the most prevalent compound might not be what the dog is actually keying in on, but rather a combination of it and other V.O.C.s together in consistent ratios to one another. We have

known for quite some time that the predominant compound in Cocaine is Methyl Benzoate MW: 136.15 Likewise the predominant compound in Heroin is Acetic Acid MW: 60.05 This, to us at least gives it the smell of vinegar.

Marijuana is a bit more tricky because it is the only narcotic we deal with that dogs detect in its natural state. Many would presuppose that THC ( Tetrahydrocannabinol ) the psychoactive ingredient in Marijuana would be what we are looking for,but THC isn't formed until heat above 185 degrees is applied. This comes after the fact of smoking, not before the fact of finding...The V.O.C.s in Marijuana are lumped together into a category called terpenes. The predominant ones and common denominators amongst them are a-pinene MW: 136.23, myrcene MW:136.23, along with limonene MW: 136.24, and B-caryophyllene MW: 204.36. ( Macias,Harper,Furton et al, 2008 )

Methamphetamine: the V.O.C.s prevalent in Meth are quite a bit harder to pin down and isolate. A quick review reveals well over ninety chemical compounds used in the various ways to manufacture Methamphetamines. Some of the more common compounds included benzaldehyde, benzyl alcohol, amphetamine, benzyl methyl ketone, and a host of others. Let it be noted that after the SPME-GC that eight area 'peaks' appeared for the various V.O.C.s These were converted to their square roots and logarithms and evaluated using Euclidian distance, cosign distance and correlation coefficient. “The numbers and intensities of the peaks were different, depending on sample”. ( Kuwayama, Tujikawa,Myaguchi,Iwata,Inoue,Kishi. Forensic Science International June 27, 2006 ) In layman's terms that means we don't have a clear answer to the dominant V.O.C.s in meth , and only rough guesses at common denominators. One of many reasons that pseudo meth is unavailable for training. Due to the prevalence and low MW of the benzenes and derivatives thereof one could hazard a guess as to its predominance. Only two compounds have been found consistently through numerous seized samples of methamphetamine.Benzaldehyde MW: 106.12, and the intermediate ketone 1-phenyl-2 propanone MW: 134.18. Benzaldehyde has demonstrated some potential in creating a pseudo meth for a training aid. ( Lorenzo, Furton et al,. 2003)

THE PERSONAL SCENT SIGNATURE

This is where V.O.C.s become very interesting and information surfaces that can be very beneficial in cases involving tracking.Regardless of source of emanation the human scent signature is basically broken down into Primary, Secondary, and Tertiary odors.

Primary odors are constituents that are basically stable over time. These are hereditary factors and comprise approximately 85% of the signature. Secondary odors are the result of environmental influences, namely diet and other factors that are on-going but subject to little change. These are responsible for approximately 10% of the scent signature. Tertiary odors are what we usually refer to as 'personal scents', soaps, shampoos, detergent, and colognes. These account for the remaining 5% of the signature, far less than we used to think. ( Curran et al,. 2005)

Again SPME-GC is used to separate and analyze the V.O.C.s that comprise the human scent signature and the key to remember here is that due to the high genetic constituent factor that the RATIOS of V.O.C.s to one another remains constant. The amounts will change day by day of course, and with changes in metabolic rates, but the ratios remain constant. This in effect makes your personal scent signature virtually as unique as your fingerprints. ( Curran et al,. 2005 )

Before we go on, read between the lines. This is what enables a tracking dog to stay on the right track through a crowded neighborhood. This is what enables a dog to cross the 'hot' track of a jogger without losing the track he is on. Likewise the acidic nature of the track of a stressed subject aids the dog, and as we shall see ( and already know, if you've been paying attention in classes) that the PH goes acidic under metabolic stress.

Sources of emanation: Samples of V.O.C.s are collected from a variety of sources, by various methods we won't need to delve into for the purposes of this article. To condense the information

though, samples are collected from the breath,Axillary ( armpit/apocrine sweat glands),Plantar ( Foot Sweat),and skin emanations ( eccrine sweat gland-thermoregulating/oils secreted on hands/fingerprints)

The breath of course is the first place scent will emanate from and since it is already in gaseous form it is readily available to the K9.The breath being body temperature will usually be warmer than the ambient temperature, causing it to rise above the body, cool and fall, leaving a “ Thermal Wake” on the track. Like the wake of a boat in water, this will gradually widen behind the tracklayer and eventually dissipate according to existing environmental conditions. ( Gary Settles; Freeman Scholar Lecture 2004 ) This wake will also of course be subject to the scent rules covered in the basic handling manual.

Other sources of emanation, the eccrine and apocrine sweat glands will of course step up production of odors as an adjunct to an increase in metabolic rate, thus further increasing the strength of the scent band, and at the same time increasing the acidity of it. Remember, acidic compounds are ever so slightly irritating to the OSNs on a dog,making the trail easily distinguishable.

As an example, 277 different V.O.C.s were found to emanate from the skin alone. Far too many to hold significant meaning for us here. So again, we will try and distill down to common denominators. Both qualitative and quantitative differences were discovered in the sampling, however the “ ratio pattern of common compounds has been shown to be distinguishable among individuals.There were significantly greater variations in the ratio of components observed among individuals tested than for one individual.” ( Curran et al,.2005)

Of these 277 compounds 32 were found to be “ Common” and of those 32 , five were found in every subject tested. While by no means comprehensive we can consider these common denominators in the personal scent signature of a human. Decanal MW: 156.2, Nonanal MW: 142.23,Phenol MW: 94.11,Tetradecane MW: 196.91, and Dodecanoic Acid-mtehyl ester MW: 200.32. Note the acidic nature of Phenol and Dodecanoic Acid.

A host of others will also be present in the personal scent signature, and we have covered these in many classes. They are most important to us again to distinguish our target tracklayer by the fact they increase greatly in volume under metabolic acidosis ( increased stress and activity) Most notable of course will be epinephrin MW: 163.20, diaminopentane MW: 102.18( emanated by bacterial decomposition of cells of a faunal nature), and diaminobutane MW:161.07( emanated by bacterial decomposition of cells of a floral nature).

An interesting footnote to the uniqueness of the human scent signature comes from a study in the Canine Behavior Research center, Czech University of life Sciences. Knowing what we now know of the human scent signature the study was conducted to see the efficacy of trained K9s to distinguish between Monozygotic and Dizygotic twins. ( Remember the 85% hereditary factor...) In short the findings were that all dogs involved could match the scent of one Monozygotic twin to a scent sample of the other. All dogs showed no discrimination between the two monozygotic twins. All dogs were able to distinguish easily the Dizygotic twins. In a track laying exercise where the monozygotic twins were laying a track side by side, then split into a Y with the dog being given a scent sample of one of the twins to follow, none of the dogs involved performed better than statistical chance. ( Dogs Discriminate Identical Twins Ludvik et al,. 2011) Very luckily we are hardly ever called upon to track a pair of monozygotic twins who have recently committed a crime....

As for the Forensic and legal implications of these findings, they remain pretty much up in the air in the U.S. Court System. This type evidence is often challenged and maintaining a “ Scent Bank” ( As is done in the Netherlands) much as we maintain a DNA Bank is considered some infringement . In order to pass muster in the U.S. Courts as 'scientific' it must pass the Frye and Kelly rules. Evidence can only be admissible if it is considered reliable in the relevant scientific community, if it is presented by a qualified expert, and if the tests conducted are utilizing proper scientific procedures. Currently K9 evidence is admitted by expert witness testimony by the dog's handler, or his certifying organization.
( Curran et al,. 2012)

EXPLOSIVES

For Explosive Ordnance Detector K9s there are no less than five compound classes and scores of compounds that can be utilized as training aids. For the purposes of this paper we will concentrate on the most prevalent ones in use. These would include the toluenes- nitrotoluene (NT) dinitrotoluene
( DNT) and 2,4,6 trinitrortoluene ( TNT).Benzenes- dinitrobenzene ( DNB) and trinitrobenzene (TNB). Others include pentaerythritol ( PETN), trinitrotriazacylohexane (RDX), tetranitrotetrazacylooctane
( HMX aka Octogen)

In many instances these compounds hereinafter referred to by their Acronyms have heavy molecular weights and correspondingly low vapor pressures making airborne molecules far less available to the olfactory capabilities of the K9. In short, truly volatile organic compounds are hard to come by in the explosive compounds per se. Likewise, due to heavy MW and slow molecular movement residue from explosive traces tends to be stable for quite some time in some cases.TNT, PETN, and RDX residue can remain on surfaces for days, and almost a third of TNT residue lasts 24 hours. The more volatile DNT left only 18% residue after 60 minutes. To us of course this equates to a dog indicating on an empty space,but one in which explosives were at least recently stored.

Along with the explosives per se are compounds which will yield V.O.C.s such as plasticizers and stabilizers ( used in the 'melt and pour' type plastic explosives) Plastics used as containers for mines etc. In addition smokeless powder of single, double, or triple base contains a number of V.O.C.s Two chemicals and their resultant V.O.C.s identified as viable training aids here are Nitroglycerine and Nitroguanidine. A caveat here is the fact that like other scents in other fields, the most volatile of the chemical compounds can cross contaminate if the explosives are stored together. This resulted in studies with dogs being able to distinguish only two of the nine odors they were initially trained on. ( Lorenzo, Furton et al,.2003)

Due again to the low vapor pressure of many common explosives compounds with high vapor pressures are often added as markers strictly to aid in detection by K9 and electronic detectors. Commonly called 'taggants', One of the more common is 2,3-dimethyldinitrobutane ( DMNB) MW: 176.17 Caveat here as well,these taggants may be found only in commercial and military explosives, often they are absent in explosives sold on the black market. If possible its wise to train with and without taggants.

With just the variables present that we have discussed thus far, it is easy to see that EOD
( Explosive Ordnance Detection) K9s will at any time be trained on perhaps dozens of scents and combinations thereof, unlike Narcotics where three or four target drugs and their derivatives are ordinarily trained. In order to train representative samples and their accompanying V.O.C.s from each basic chemical class of explosive the following would be required: an acid salt such as ammonium nitrate ( AN ) ever popular for the Home made explosive ANFO ( Ammonium Nitrate Fuel Oil), an aromatic nitro ( TNT), a nitrate ester ( PETN), a nitramine ( RDX), an aliphatic nitro ( DMNB) and a peroxide Triacetone Triperoxide ( TATP ) another popular home made explosive.

Now more distillation is required to pare these down to the primary V.O.C.s found in the more common explosives. Samples using SPME-GC were taken from the 'headspace' above a given explosive ( basically the same air that a dog would be sampling through olfaction) with the following findings: ( Harper, Furton et al,.2005)

TNT Cast Explosives-The Primary V.O.C. was DNT MW: 182.14 secondary was Dinitrobenzene MW: 168.11

Poly Bonded ( Plastic Explosives)- The Primary V.O.C. 2,ethyl-1 hexanol MW: 130.23 secondary was the taggant DMNB MW:176.17 A distant tertiary V.OC was cyclohexanone MW:98.15 It should be

noted that there were no traces of the parent explosives in the headspace ( again presumably due to heavy molecular weight and slow molecular movement.

Single Based Powder-Primary VOC -DNT MW: 182.14

Double Based powder-No Primary or dominant VOC- Dinitroglycerine and Trinitroglycerine MW: 227.09

HUMAN REMAINS DETECTION ( HRD)

HRD is in a class by itself as far as V.O.C.s are concerned. Over 400 V.O.Cs have been identified as coming off of Human remains. They vary with every possible variable introduced into the scenario. The stage of decomposition, depth or lack thereof of burial, water, temperature, humidity , and virtually everything else that comes to mind.

Again, 'common denominators ' out of thus huge list have been identified. Documented in peer review literature as viable V.O.C.s in HRD are the following categories and corresponding numbers present: Acids/esters-20,Alcohols-15,Halogens-10,Ketones-11,Aldehydes-14, Cyclic Hydrocarbons-21, Straight Chain hydrocarbons-10,and Sulfides-11. Confusing enough for you? More distllation coming... ( DeGreeff, Furton et al,.2011 )

Five standard compounds have been previously cited as being Human Remains volatiles and they represent a range of the functional groups mentioned above. These are: n-butyric acid MW:88.11, heptanoic acid MW: 130.18, 6-methyl-5-hepten-2-one MW: 126.19, liquified phenol MW: 94.11, and nonanal MW: 142.24 ( Sigma Aldrich Company, St. Louis, MO. USA) One can only assume that these five are part and parcel of Sigma Aldrich Pseudo Corpse Training Scents 1 through 4. These training scents are used in venues where actual body parts cannot be used or are illegal ( i.e. Japan, California, and a variety of Public Demonstrations for purposes of decorum) and have proven extremely effective.

Any discussion of HRD would be incomplete without covering two V.O.C.s we also find present in the Human Scent Signature. Cadaverine aka diaminopentane MW: 102.18 , a metabolic waste product from the bacterial and microbial decomposition of faunal cells and Putrescine aka diaminobutane MW: 161.07 which is a metabolic waste product from the bacterial and microbial decomposition of floral cells. Both chemicals are odiferous , and indeed toxic in large quantities.

REFERENCES

Collection and Identification of Human Remains Volatiles by non-contact dynamic airflow sampling and SPME/GC/MS using various sorbent materials. Lauren E. DeGreeff, Kenneth Furton. June, 2011

Comparison of the Volatile Organic Compounds Present in Human Odor Using SPME/GC/MS Allison M. Curran, Scott I. Rabin,Paola A. Prada, and Kenneth Furton. Journal of Chemical Ecology, Vol.31 No.7 July 2005

The Differentiation of the Volatile Organic Signatures of Individuals Through SDPME/GC/MS of Characteristic Human Scent Compounds. Allison M.Curran PhD : Paola A. Prada B.S.; and Kenneth G. Furton PhD. Journal for Forensic Sciences January 2010 Vol.55

Laboratory and field experiments used to identify Canis Lupus var.Familiaris active odor signature

chemicals from drugs, explosives, and humans. Norma Lorenzo,Tian Lang Wan, Ross J. Harper, Ya-Li Hsu,Michael Chow,Stefan Rose, Kenneth G. Furtion Special Issue Paper July 4,2003

Sniffers: Fluid Dynamic Sampling for Olfactory Trace Detection in Nature and Homeland Security-The 2004 Freeman Scholar Lecture .Gary S. Settles Penn State University March 2005

Dogs Discriminate Indentical Twins Ludvik Pinc,Ludek Bartos,Alice Reslova,Radim Kortba Open Access June 2011

Identification of dominant odor chemicals emanating from explosives for use in developing optimal training aid combinations and mimics for canine detection. Ross J. Harper, Jose R.Almirall, Kenneth G. Furton . Elsevier July 2005

Identification of volatile chemical signatures from plastic explosives by SPME-GC/MS and detection by ion spectrometry Hahn Lai,Alfred Leung,Matthew Magee, Jose R. Almirall Original Paper March 2010

Characterization of the volatile organic compounds present in the headspace of decomposing human remains. Erin M. Hoffman,Allison M. Curran,Nishran Dulgerian,Rex.A. Stockham,Brian A. Ekenrde Forensic Science International February,2008.