Chemistry Unit

Kerri Heward, Supervising Criminalist
Desk Phone: (775) 328-2803
kheward@washoecounty.us

The Chemistry Unit performs various examinations that are divided into four sub-disciplines.  These examinations have been traditionally placed in controlled substance or trace evidence disciplines.  Examinations that are not encompassed in these four sub-disciplines, such as other trace evidence type examinations including paint, fiber, glass, and explosive examinations, are not performed by the Forensic Science Division.

General Unknown Sub-Discipline

Overview of Services

This sub-discipline involves analysis, comparison, general classification, and sometimes identification of unknown substances.  This type of examination can be performed on a wide variety of samples including powders, liquids, adulterants, residues, and stains.  The scope of general unknown examinations typically is not intended to serve as screening for completely unknown materials.  Instead, this type of examination is best utilized when some information about the type of substance is known and provided to the Forensic Science Division. 

In cases involving only questioned samples, the examination performed will attempt to determine the identity of the sample and possible sources of the sample.  In cases involving both questioned and known samples, a detailed comparison of various physical and chemical properties will be performed and the examination also will attempt to determine the identity of the samples. 

The Forensic Science Division has limited analytical techniques that can be employed in general unknown examinations; thus, the services provided or the conclusions that can be drawn may be restricted, especially for some samples or compounds.  When these situations arise, the reported results will include any pertinent qualifying information or restrictions that have been encountered as a result of the available analytical techniques or due to the sample itself.  Sometimes a meaningful examination or comparison may not be achievable in general unknown submissions.  

Methods

The following examinations or tests may be employed in general unknown examinations:

• Macroscopic (i.e. visual) examinations
• Microscopic examinations
• Chemical tests including spot or color tests, microcrystalline tests, solubility tests, miscibility tests, and pH measurements
• Extraction, separation, and concentration techniques
• Fourier transform infrared spectroscopy (FTIR)
• Gas chromatography/mass spectrometry (GC/MS)
• Gas chromatography with a flame ionization detector (GC/FID)
• Photography

 

Submission of Evidence

Prevention of cross-contamination is critical with any evidence, but especially with evidence submitted for general unknown examinations.  Specific packaging recommendations often depend on the nature of the sample.  Contact the Forensic Science Division with any packaging and submission questions prior to submitting general unknown evidence.

Specific information about the case circumstances and the type of material suspected or of interest in the case should be provided when submitting evidence for general unknown examinations. 

Comparison samples and reference materials should be provided when possible.  The absence of such materials may limit the conclusions that can be drawn from a general unknown examination.

Any potentially hazardous materials must be appropriately labeled.

Liquid samples should be placed in glass jars or vials that have a Teflon lined, not paper lined, lid.  Metal cans generally are not suitable as the primary container for liquid samples, because the cans rust which can result in leakage.

 

Ignitable Liquid Sub-Discipline

Overview of Services

This discipline involves the analysis of various types of samples, including fire debris and liquids, for the presence of ignitable liquids.  Various types of materials or products contain ignitable liquids or are ignitable liquids.  Gasoline is the most common ignitable liquid, but many others exist.  Ignitable liquids have many different legitimate uses. 

Ignitable liquids can be used to initiate a fire; thus, many samples submitted for ignitable liquid analyses consist of debris from a fire.  Liquid samples suspected to contain ignitable liquids or clothing items, including shoes, are sometimes submitted for ignitable liquid examination. 

The examination performed will attempt to determine if any ignitable liquid is present in a sample and provide a classification of any detected ignitable liquid.  Sometimes it may not be possible to determine the potential source of compounds detected in the ignitable liquid examination, especially if appropriate comparison samples were not submitted.

Identification of specific sources or brand identification of ignitable liquids is not performed, because of the nature of the production and distribution of ignitable liquids. Comparison of different ignitable liquids may be performed, but the conclusions drawn may be limited, again for the same production and distribution reasons.

Methods

The following examinations or tests may be employed in ignitable liquid examinations.

• Extraction, separation, and concentration techniques
• Gas chromatography/mass spectrometry (GC/MS)
• Gas chromatography with a flame ionization detector (GC/FID)
• Macroscopic, i.e., visual examinations
• Microscopic examinations
• Fourier transform infrared spectroscopy (FTIR)

 

Submission of Evidence

Any evidence submitted for ignitable liquid examination must be packaged in an appropriate airtight container, because most ignitable liquids are fairly volatile.  The Laboratory can elect to not examine ignitable liquid evidence not packaged correctly.  Appropriate airtight containers include metal cans and special heat sealed plastic packets specifically made and marketed for packaging ignitable liquid evidence.  Heat sealing is the most effective technique to seal plastic packets.  The Forensic Science Division can provide additional information on proper packaging materials and potential sources of these materials.  Paper bags, manila envelopes, and general use plastic bags, e.g., zip-lock plastic bags and trash bags, are not suitable packaging materials for ignitable liquid evidence.  Avoid over filling containers.  In general, the sample should fill no more than ¾ of the volume of a container.  Sharp objects should not be placed in heat sealed plastic packages.   

Liquid samples should be placed in glass jars or vials that have a Teflon lined, not paper lined, lid.  Metal cans generally are not suitable as the primary container for liquid samples, because the cans rust which can result in leakage.

Comparison samples should be submitted when possible.  A comparison sample consists of a sample as similar to the evidence sample as possible, except that the comparison sample is believed to be free of any ignitable liquids.  For example, if the evidentiary sample consists of a piece of carpet suspected to contain an ignitable liquid, the comparison sample should consist of a piece of the same type of carpet that is not suspected to an ignitable liquid.  Comparison samples also should be packaged in airtight containers, preferably using the same type of container used for the corresponding evidentiary sample.  The lack of comparison samples may limit the conclusions that can be drawn from an ignitable liquid analysis.

Because of the volatile nature of ignitable liquids, evidence collected for ignitable liquid examination should be submitted to the Forensic Science Division as soon as reasonably possible.  Soil substrates and some other materials may contain microbes that can degrade any ignitable liquids present in a sample.  It is even more imperative that these samples are submitted in a timely manner. To minimize microbial degradation, samples can be refrigerated or frozen.  Significant microbial degradation can occur in five days or less.

 

Physical Match Sub-Discipline

Overview of Services

Whenever items are cut, torn, broken, or otherwise separated into two or more pieces, a unique break can be created due to the randomness of the separation process.  Physical matching is the total or partial reconstruction of a broken object using the unique features at the edges that are a result of the separation process.  Physical matches are also known as fracture matches or mechanical fits.  When pieces of a broken object can be reconstructed in this way, unequivocal identification of source can sometimes be established.  The strength of the association is dependant upon the nature of the material and the amount and uniqueness of the features and irregularities at the broken edges.

Solid materials such as glass, porcelain, plastic, and metal provide the greatest likelihood for an unequivocal match.  Other materials such as tape, paper, wood, and cloth are likely to provide some information and some degree of association, but an unequivocal match may not be possible as the separation process may not have produced sufficient unique features.  

Methods

The following examinations or tests may be employed in physical match examinations.

• Macroscopic (i.e. visual) examinations
• Microscopic examinations
• Photography

Submission of Evidence

When submitting evidence for a physical match examination, it is important to submit as many of the broken pieces as possible; not just the largest ones. Often the smaller pieces can be the most valuable.

Items submitted for physical match examinations must be packaged carefully to avoid any further breakage and any damage to the pieces.

The items must be labeled in a manner that clearly establishes the location of recovery.

 

Seized Drug Sub-Discipline

Overview of Services

This sub-discipline performs qualitative analyses of samples for the presence of controlled substances.  A wide variety of materials are encountered as samples including powders, liquids, vegetable and plant materials, paper, and items containing or bearing residue.  The most commonly encountered controlled substances are methamphetamine, marijuana, cocaine, and heroin. 

     

Sample limits and testing protocols have been established and are employed in seized drug casework submissions as follows:

• Tests performed include qualitative analysis and identification of substances controlled under the Federal Controlled Substances Act (CSA) or the Nevada Administrative Code (NAC).
  • Up to five different items can be submitted in a case.  For cases involving more than five items, contact the District Attorney handling the case and the Forensic Science Division prior to submission.
  • Evidence will be accepted in cases that are being actively prosecuted or in cases for which the testing results will be used at a Grand Jury, to substantiate charges that will be filed or are pending, to obtain a warrant, in an on-going investigation or for officer safety.
     
• Only selected items from those submitted will be analyzed.
  • Multiple items that are visually similar in appearance and packaging only will be tested when the total net weight could substantiate a trafficking charge. This analysis may be deferred until the case is set for District Court.
  • When multiple substances likely to contain a Schedule I compound are submitted, one of each type of substance will be analyzed.
  • When a Schedule I compound is identified, substances likely to contain a compound in a lower schedule will not be analyzed.
  • Items bearing or containing residue only and paraphernalia items only will be tested when no other controlled substance evidence exists, when other items do not contain a controlled substance, or at the special request of the District Attorney handing the case.

 

• A specific testing approach has been established for pharmaceutical preparations (tablets or capsules).
  • Only a visual examination with comparison to a database will be performed when a scheduled controlled substance (except marijuana) is identified in a non-pharmaceutical preparation.
  • Analysis and identification of a controlled substance in one dosage unit of the pharmaceutical preparation will be performed when no other controlled substance in a higher schedule exists in the case (except marijuana).
  • Only a visual examination will be performed for pharmaceutical preparations consistent with preparations containing a prescription only or over-the-counter compound.

If services beyond those listed above are needed, please contact the Forensic Science Division for consultation prior to submitting the evidence. 

A few general comments bear mentioning.

• Services provided only include qualitative testing.  This type of testing identifies any controlled substances present in a sample. 
• The services provided do not include quantitative testing.  This type of testing determines the amount of a compound in a sample and is usually expressed as a percentage.  This testing is not performed as it is not relevant based on the current language in the Nevada Administrative Code (NAC).
• The services provided do not attempt to identify any non-controlled substances such as cutting agents, excipients, over-the-counter compounds, or prescription only compounds.

Syringes/hypodermic devices are not analyzed unless extenuating circumstances exist and the analysis is approved by the Division Director or her designee prior to submission. 

Any suspected marijuana that has visible signs of mold will not be analyzed as the mold associated with marijuana is a known carcinogen. If wet vegetable material is recovered, e.g., live plants, it is critical to completely dry the vegetable material prior to packaging it, even if it will be packaged in cardboard boxes or paper bags.

Limited analytical services are provided in clandestine laboratory cases.  The provided services include analysis and identification of precursors, such as ephedrine or pseudoephedrine, and controlled end-products, such as methamphetamine.  No analytical or testimonial services are provided for manufacturing methods, by-products, or other starting materials.  Prior to submitting any evidence from a clandestine laboratory, please contact the Forensic Science Division to discuss the case. Also, consultation with the District Attorney handling the case is an integral part of a clandestine laboratory case.

Very limited analytical services are provided in analysis of suspected steroids in seized drug cases.  The Forensic Science Division does not have reference materials for the numerous steroid compounds; thus, no identification of steroid compounds will be made.

The laboratory does not test paper currency for the presence of controlled substances.

Methods

The following examinations or tests may be employed in seized drug analyses:

• Macroscopic (i.e. visual) examinations
• Microscopic examinations
• Weight measurements
• Screening (i.e. presumptive) tests including color tests
• Chemical tests including microcrystalline tests, solubility tests, and miscibility tests
• Extraction, separation, and concentration techniques
• Fourier transform infrared spectroscopy (FTIR)
• Gas chromatography/mass spectrometry (GC/MS)
• Gas chromatography with a flame ionization detector (GC/FID)

    

Submission of Evidence

Packaging and submission of seized drug evidence should follow some general guidelines that are provided below. 

• The safest guiding principle for packaging seized drug evidence is to package the items such that the natural order and appearance is preserved for presentation in court. The way the evidence was packaged should not create confusion for the jury. Similar items from one location, such as several bindles from the same drawer or pocket, present less confusion packaged together. Items logically separated by space and time should be packaged separately to avoid confusion.


• Clear plastic evidence bags are recommended for inner packaging as they allow the evidence to be viewed in court without opening the bag. When sealing evidence in these bags, allow sufficient room for opening for analysis and resealing after analysis.


• Clearly mark all packaging with any hazard associated with the evidence, such as biohazard,when the evidence was recovered from a body cavity or from fecal matter.


• Generally, syringes are not accepted.  For cases involving syringes, please empty the contents of the syringe into a vial and submit only the vial containing the liquid sample.


• Non-controlled substance items should not be packaged with suspected controlled substances.  Examples of non-controlled substance items are clothing, identification cards, compact discs, and tools.  Pharmaceutical preparations, i.e., tablets and capsules that do not contain a controlled substance should be packaged separately as a non-controlled substance item. Even if these items were recovered with the suspected controlled substance, separate the items before submitting them to the Forensic Science Division and only submit the items relevant to the requested examination.


• Items that do not require seized drug analysis should not be submitted or packaged with the evidence that will be analyzed.


• Items that contain residue or are paraphernalia should be packaged separately from other seized drug evidence.  These items generally are not analyzed when other seized drug evidence exists.


• Used field test kits should not be packaged with the suspected controlled substance. The Forensic Science Division does not use or need the used field test kit.  If your agency requires retention of the used field test kit, package it separately and do not submit it to the Forensic Science Division.


• Each item or package of similar items should be given a unique identifier or number. 


• Each item contained in a package must be described in the listing of the package contents.


• The gross weight, e.g., a weight that includes the substance and the packaging, of the seized drug item should be recorded and listed in the item description.  When seized drug evidence is packaged in glass containers, it is best to not include the glass container when making the weight measurement.


• Vegetable or plant material must be thoroughly dried prior to packaging or the material may start to mold and rot. If the plant material is recovered wet, thoroughly air dry the material at room temperature prior to packaging and submitting.  Significant mold can form in five days or less on wet or damp plant material.  After drying, the plant material should be packaged in paper or cardboard to allow breathing and further drying of the material.


• Roots, soil, and any other non-vegetative material should be removed prior to packaging plant materials.


• Liquid samples should be placed in glass jars or vials that have a Teflon lined, not paper lined, lid. Metal cans generally are not suitable as the primary container for liquid samples, because the cans rust which can result in leakage.