chemistry. chemistry is 1 of the 5 major science classifications with others being biology, physics,...

Chemistry

Chemistry

• Chemistry is 1 of the 5 major science classifications with others being biology, physics, earth science & space science.

• Chemistry is the science that treats the composition of substances & their transformation, the reactions by which they undergo change into other substances.

Chemistry

• Chemistry’s analytical aspect deals with determination of the exact composition of substances – called chemical analysis.

• Chemical analysis has two major divisions: qualitative analysis, which seeks to determine what elements or compounds may be present, & quantitative analysis, which attempts to determine relative amounts of each.

Chemistry

• By 1814, with the publication of his treatise on poisons, Mathieu Orfila established toxicology, a branch of forensic chemistry, as a legitimate scientific discipline.

• As one of the major subdivisions of science, it is not surprising that chemistry continues to be a mainstay of criminalistic procedures.

Chemistry

• How Chemistry is used in Forensics: fingerprint expert may use a chemical such as ninhydrin to develop latent thumbprint; firearms examiner may employ chemical methods to detect lead residue around a bullet hole or apply etching reagent to restore serial number; specialist in questioned documents may utilize thin-layer chromatography to identify certain brand of ink; the microscopist may use microchemical techniques in analysis of trace evidence, etc.

Chemistry - Drugs

• We can apply chemistry in investigations regarding drugs, toxicology, arson & explosives.

• Our primary concern is that of the forensic chemist with identification of illegal drugs. Such drugs may be divided into 4 major types: narcotics, depressants, stimulants & hallucinogens.

Chemistry - Drugs

• Narcotics: from Greek narkotikos (“ to benumb”) has become loosely applied to a variety of drugs.

• True narcotics are drugs that relieve pain through depression of the central nervous system and sleep.

• Most narcotics derived from opium from oriental poppy plant & primarily grows in Asia, Mexico & the Balkans

Chemistry - Drugs

• Opium is in the form of a milky substance obtained by slitting open the unripe poppy pods. Raw opium is pressed into cakes that are naturally dark brown or black.

• This material is used to make the opium that is sold on the market, a dark-brown extract produced by a process of boiling, fermenting & roasting.

Chemistry - Drugs

• The finished product may be chewed, eaten or smoked.

• Medicinal forms include an opium solution known as laudanum, which was a popular analgesic (painkiller) during the 18th & 19th centuries and liquid, powder & granulated forms of modern medicinal opium.

Chemistry - Drugs

• Opium derivative narcotics include morphine, codeine, and heroin.

• Morphine (morphine sulfate) is an important medical analgesic that accounts for about 12% of raw opium.

• Legal form is typically a 1-grain white tablet. Illegal drug is usually in the form of a white powder.

Chemistry - Drugs

• It can be taken orally, a method that addicts regard as wasteful, or it can be “mainlined” (injected directly into the bloodstream) by dissolving the drug in water placed in a spoon & heated.

• The solution is commonly injected by a needle attached to an eyedropper with a rubberband instead of conventional syringe.

Chemistry - Drugs

• Although codeine is actually found in opium, it typically is made synthetically from morphine. Its strength is only 1/6 that of morphine so it is not a popular street drug.

• It is primarily used as a cough suppressant in cough syrup and is sometimes the source of sporadic & minimal abuse by juveniles

Chemistry - Drugs

• Heroin is a derivative of morphine (made by reacting it with acetyl chloride or acetic anhydride).

• It is the drug that most commonly results in cases of narcotic addition. It is usually a white, crystalline powder, but occasionally may be found in tablet or cube form.

• It is used in essentially the same way as morphine – a users “kit” (spoon, etc.)

Chemistry - Drugs

• Among the narcotic drugs that are not derived from opium – drugs known as synthetic opiates – the most common is methadone (methadone hydrochloride).

• Although it is related to heroin, methadone tends to eliminate an addict’s craving for heroin while at the same time causing only minimal side effects.

Chemistry - Drugs

• It’s sometimes used in treating heroin addiction to relieve withdrawal pains, even though it is capable of being addictive. Other names for it: Adanon, Amidon, Amidone, Dolophine & Methadon.

• Other synthetic opiates: meperidine hydrochloride (Isonipecaine, Demerol) & dihydromorphinon hydrochloride (Dilaudid)

Chemistry - Drugs

• Depressants are drugs that have a depressing action on the central nervous system.

• Most widely used and indeed the most widely used and abused drug in the world today is alcohol.

• Estimated 50% of those committing fatal assault are intoxicated as are those committing suicide

Chemistry - Drugs

• Some 40% of victims of homicidal assault are likewise in a state of intoxication

• Barbiturates, major depressant category, commonly called “downers” because of their ability to cause one to relax, experience a feeling of well-being & lapse into sleep. Proper dose may be medically beneficial, an overdose may cause death.

Chemistry - Drugs

• Barbiturates are often the drug of choice for those intending suicide.

• They are also addictive & produce a withdrawal syndrome more severe than any other drug.

• Barbiturates are derivatives of barbituric acid & include phenobarbital, sodium Amytal, Nembutal & Seconal

Chemistry - Drugs

• Nonbarbiturate depressants known as methaqualone (Sopor & Quaalude) - a powerful sedative; tranquilizers such as meprobamate (Miltown & Equanil), chlordiazepoxide (Librium) & diazepam (Valium) and chloral hydrate (a.k.a. “knock-out drops”).

Chemistry - Drugs

• There are also certain volatile solvents that can depress the central nervous system when “huffed” or sniffed (as in glue sniffing) including toluene, gasoline, naphtha, trichloroethylene & methyl ethyl ketone.

Chemistry - Drugs

• Stimulants are drugs like amphetamines commonly known as “uppers” or “speed” that stimulate the central nervous system & provide increased alertness followed by a decrease in appetite.

• Serious abuse often begins when either amphetamine or its chemical derivative methamphetamine is injected into a vein.

Chemistry - Drugs

• Another major stimulant is cocaine, once used as medicinal local painkiller. Extract of leaves of the coca plant, cocaine is a white crystalline alkaloid powder.

• Today’s processed cocaine is typically sniffed or injected whereas the past was used to relieve pain & fatigue by chewing leaves or brewing a tea. Side effects in extreme cases: hallucinations & paranoia

Chemistry - Drugs

• Hallucinogens: mood & perception-altering drugs that may produce hallucinations

• Natural: peyote, mescaline & psilocyban.

• Synthetic: LSD, DMT, & STP

• LSD was a popular mind-expanding drug of the 60’s & is reportedly “the most powerful hallucinogen yet developed”.

Chemistry - Drugs

• A relatively mild hallucinogen comes from the female hemp plant which produces a resin that is sold in pure form and is known as hashish.

• The leaves (& often seeds, stems, etc.) are the most common form & represent the drug marijuana.

Chemistry - Drugs

• Hashish usually smoked in special pipe.

• Marijuana typically made into cigarettes called “reefers” or “joints” and is “the most widely used of the illicit drugs.”

• Drug tests: The forensic identification of “controlled substances” & other drugs begins with screening tests.

Chemistry - Drugs

• Field tests are usually spot tests where a small amount of questioned substance is placed in well of a spot plate & one or more chemical reagents is added.

• Lack of reaction is interpreted as absence of drug being tested; Positive reaction, usually color change, is indication the substance may be drug in question with further tests required.

Chemistry - Drugs

• Other preliminary tests: Microscopic analysis (marijuana & drugs with micro-crystals of distinctive shape & color); Ultraviolet spectrophotometry (based on comparison of UV spectra with compilations of such spectra)

• Following screening tests (reduce possibilities of questioned substance) come certain confirmatory tests.

Chemistry - Drugs

• Most common confirmatory tests are infrared spectrophotometry & gas chromatography-mass spectrometry.

• Infrared spectrophotometry based on tendency of even very similar substances to exhibit different infrared spectra.

• The unknown spectra is compared to a “library” of spectra from known compounds

Chemistry - Drugs

• Gas chromatography-mass spectrometry is powerful technique resulting from combination of 2 analytical methods in a single instrument.

• It first separates the various components of a possibly complex drug mixture, then unequivocally identifies each of them.

Chemistry - Toxicology

• Study of poisons = toxicology. Mathieu Orfila is creator of forensic toxicology.

• Originally, the science consisted largely of the attempted detection & identification of poisons in cases of suspected homicide.

• Today, suicides & “accidental” suicides make up the bulk of the toxicological work carried on in the West.

Chemistry - Toxicology

• That is true only of “classic” toxicology.

• Modern toxicologist has been assigned the job of testing blood & urine for alcohol (most common substance tested for in most police labs) in suspected cases of DUI. Testing may also be done for drugs.

• Topics of discussion: alcohol & drugs and poisons in death investigations

Chemistry – ToxicologyAlcohol & Drugs

• To measure the level of blood alcohol, samples of blood, breath or urine may be taken, depending on the jurisdiction.

• Blood: alcohol/drug testing preferred specimen must be taken in medically approved manner.

• Alcohol must not be used to clean syringe since it might affect the test results.


• A nonalcoholic cleaner should be used on area of skin where sample is drawn. 10-20 ml of blood should be drawn in container supplied for the purpose & containing an appropriate anticoagulant & preservative.

• Urine samples to be tested for alcohol or drugs are collected after subject has first voided the bladder & waited about 20 minutes.


• Urine is then collected in a container with appropriate preservative. A collected sample of about 25 ml is recommended.

• For both blood & urine, an officer should observe the procedure, mark the evidence appropriately, & submit it to the lab to be tested.


• Breath samples used for alcohol tests only, are not transported to the lab.

• Field collecting instruments such as the Breathalyzer analyze the specimen using a sort of specialized spectrophotometer.

• In general, lab tests for blood can be applied to other biological samples such as urine.


• Early testing methods tend to be chemical.

• Today most widely used techniques to identify alcohol in forensic lab are gas chromatographic methods.

• Basic procedure involves vaporizing specimen, injecting resulting gases into inert carrier like nitrogen gas, through special tube.


• Different constituents exit at different retention times & can be measured & are characteristic for known constituents.

• Analysis of blood or urine for alcohol requires only a single drop. In a few minutes an instrumental pen trace shows whether or not alcohol is present & if so, what amount.


• Blood specimens obtained from deceased person require special procedures since bacterial action can produce ethyl alcohol during the process of decomposition.

• In case of biological fluids/tissues pH of drugs are considered. Acidic: barbiturates & aspirin; Alkaline (basic): amphetamines, cocaine, methadone & PCP.


• Once separated into acidic and basic, two step process of screening & confirmation.

• Common screening tests are thin-layer chromatography (TLC) & gas chromatography (GC), as well as another screening tool called immunoassay, which is specific antigen-antibody reactions like those used in blood typing.


• The preferred confirmatory choice is gas chromatography-mass-spectrometry, described as a “one-step confirmation test of unequaled sensitivity & specificity”.

• When person dies & question of poison involved, pathologist sends samples of body tissues & fluids to the lab for analysis by a toxicologist.

Chemistry – ToxicologyPoisons in Death Investigations

• Samples should contain 3 ounces of blood without preservative; all of the stomach contents (in some cases stomach itself); ½ of liver; both kidneys; all of the urine from bladder; & ½ of brain.

• Blood should be taken from both bottom chambers of heart as well as other sites in the body.


• Lungs & Entire brain are taken if a volatile poison is suspected (one that evaporates rapidly), & the spleen if cyanide is indicated.

• Even if the body is skeletonized, arsenic may be detected from the hair, nails & bone particularly a segment from the femur (largest bone in the body).


• Circumstances that may point to poisons include corrosion or burns about mouth, presence of drugs or drug paraphernalia at scene, or fact that victim was potential target by virtue of being burden on others.

• Any medicines or substances found near victim, along with cups, drinking glasses or other containers should be collected at the scene as potential evidence.


• Per experienced homicide investigator: “The most important fact to keep in mind is that the scene examination & investigation into the events leading to the death must be thorough & complete.”

• The medico-legal autopsy will determine type & quantity of poisonous substance involved. Cause of mode of death will be based on police investigation at the scene.

Chemistry – Toxicology


• Today’s toxicologist is largely dependent on a battery of analytical techniques using various forms of chromatography, complex & electronic machines with results in form of either a graph or in a computer printout as in ultra modern instruments.

• Several methods for different jobs.


• Gas chromatography, paper & thin layer chromatography, & most recent high pressure liquid chromatography (HPLC).

• HPLC can detect tiny traces of formerly “difficult” substances as LSD in urine & monitor strength present by process known as radioimmunoassay. Sample need be no more than .000000001 grams


• Toxicologist may play important role in investigation of fires. If decedent were to have less-than-fatal level of carbon monoxide in his/her blood, it could indicate person was dead before the fire began.

• Elevated levels of carbon monoxide also can be caused by smoking & living in a polluted environment.


• Any of various chemicals found in the decedent’s blood could indicate the person was breathing them in with smoke from fire & was alive at the time.

• Nature of chemicals may indicate an accelerant was used (example: presence of nitrous oxides would point to nitrogen-containing fuels).

Chemistry – Arson

• Incendiary fires (deliberately set) quite often involve use of accelerants, something used to promote & spread fire.

• Accelerant may be a solid, liquid or gas.• Solid accelerants range from simple

materials like paper or trash to solid chemical incendiaries such as flares, black powder or mixtures like paraffin, an oxidizer, or sugar or chlorate.

Chemistry – Arson

• Liquid accelerants are more frequently encountered & include such flammable liquids as petroleum products (gasoline, kerosene, fuel oil, etc.), alcohols, paint thinners, industrial solvents, & ether.

• Such liquids may be sloshed about an area or used in a firebomb such as a “Molotov cocktail.”

Chemistry – Arson

• Gas accelerants, such as natural gas or propane, are less commonly used. The simple disconnecting of gas line is one readily available source for gas accelerant.

• Incendiary device is typically used with the accelerant. Device may be something as simple as candle; anything that combines a means of ignition & time delay. (light candle, burns down to reach accelerant)

Chemistry – Arson

• Other incendiary devices range from simple fuses to highway flares, smoke grenades & “Molotov cocktails”

• From open book of matches with lit cigarette behind them, to spontaneously combusting chemical mixes

• Electronic devices with possible items like kitchen timers, wires, batteries, etc.

Chemistry – Arson

• The usual rules of documenting, collecting & preserving evidence apply to arson investigations.

• ATF: Bureau of Alcohol, Tobacco & Firearms involved with arson cases.

• Key to successful examination of arson evidence begins with scene investigator being able to recognize, collect & properly package evidence for lab assistance.

Chemistry – Arson

• Trained arson investigator will package his evidence in clean vapor-tight containers such as screw-cap glass jars, metal cans, or unused paint cans with tight fitting lids.

• With proper packaging, loss of accelerant is avoided & potential cross-contamination is eliminated making lab examinations to be made with reasonable chance of success.

Chemistry – Arson

• Some of materials used to start fire may be destroyed during the actual starting of the fire. Wires, batteries & other items may survive relatively intact as may neck of bottle containing remains of a wick.

• Careful searching may even reveal pool of wax remaining from candle.

Chemistry – Arson

• Place to look for traces of any incendiary device &/or fire set is at point of origin of a fire when it can be determined by arson investigator.

• Telltale residues may be soap, ash or residues of certain commercial materials.

• Lab analysis of evidence from suspected arson fires is largely accomplished by means of gas chromatograph.

Chemistry – Arson

• GC is considered “the most sensitive & reliable instrument for detecting & characterizing flammable residues.”

• Usual procedure is to heat airtight evidence container so volatile residues will be driven off collected material & be trapped in container’s “headspace” (enclosed air space). Vapor can be removed with syringe & injected into GC.

Chemistry – Arson

• Analytical chromatogram results may be compared to known standards to prove for instance, presence of gasoline indicated.

• Headspace exams may lead to # of “false negatives” or failure to detect a flammable liquid present in evidence.

• This occurs most often with low volatility such as kerosene or fuel oil.

Chemistry – Arson

• Low vapor pressure accelerants limit loss through evaporation at fire scene if not completely burned & can be recovered from physical evidence.

• Gasoline on most nonporous surfaces is rapidly lost either through burning or evaporation during or subsequent to the fire. Absorbent surfaces retain even gasoline well.

Chemistry – Arson

• If unburned residual liquids are collected, they may be recovered by separating them from substrate using variety of available techniques depending primarily on type of substrate rather than suspected liquid.

• Most widely used lab technique for this is steam distillation. Other techniques are vacuum distillation, solvent extraction, solvent rinsing & air flushing.

Chemistry – Arson

• Solvent used for extraction must be eliminated before testing.

• This is done by evaporation & using a solvent with a low boiling point to help minimize loss of suspect flammable liquid.

Chemistry – Explosives

• In the past, bombings tended to be rare & to be aimed at limited targets.

• In “Roaring Twenties”, dynamite bombs were largely province of political anarchist who targeted rich & powerful or of workers in fierce battles to establish unions.


• In 1930s, stench or stink bombs were used by gangsters to intimidate owners of movie theaters & restaurants into selling out to the Mob.

• Explosive bombs were used if owners refused.

• Rarely were bombs aimed at the general public.


• That changed on November 1, 1955, with the midair explosion of United Airlines flight 629, just 11 minutes into departure from Denver’s Stapleton Airport.

• Wreckage scattered over 5 mile area in any direction.

• Characteristic odor persuaded investigators that a bomb was responsible.


• Skin of fuselage was bent outward around a hole indicating explosion took place inside plane at that location. Several metal fragments bore gray & black deposits.

• Analysis at FBI lab showed deposits consisted of sodium carbonate together with traces of sulfur & nitrate compounds, expected residue from dynamite.


• A fragment of 6 volt battery was identified.

• Investigation led to Jack Graham, man who had taken out several large travel insurance policies on his mother who had perished in the crash.

• Search of home turned up yellow-insulated wire like that collected at crash site & identified as part of the detonator.


• He was executed in Colorado’s gas chamber on January 11, 1957.

• Explosives may be divided into two types: high and low.

• Low explosives are those that yield energy wave transmitted with relatively low frequency, only a few thousand feet per second.


• They emit a low-frequency sound as well typically described as a “pop”, “puff” or “boom” & cause relatively small damage such as gasoline & gunpowder.

• High explosives have velocities up to 25 thousand feet per second, emit a piercing high-frequency blast & create an explosive crater. Examples: dynamite & nitroglycerin


• Another way: classifying explosives by source• Military explosives are usually based on TNT or

an explosive called RDX. Another military explosive is known as PETN.

• Commercial explosives range from black powder & ammonium nitrate-fuel oil (ANFO) both used for blasting to various explosive gels & high explosives like dynamite & nitrostarch.


• Improvised explosives frequently include simple mixtures like homemade black powder & fuel mixed with an oxidizer.

• Usually are low explosives, requiring confinement to have effective blasting power. Rarely high explosives improvised

• Bomb-scene searches are similar to those of arson.


• Both involve a focal point (point of origin) & both involve evidence that’s largely destroyed, & any remaining traces need to be searched for diligently.

• Traces include explosive residues, metal fragments from a pipe, remnants of fuse or blasting cap, bits of wire &/or insulation, pieces of electrical tape, fragments of batteries, various parts of clocks or timers.


• Because the construction of a bomb is largely dictated by the available materials, the ingenuity & skill of the maker, the investigator cannot anticipate what maybe recovered in a careful scene search.

• Despite destruction & disruption, few other crime scenes provide as much potentially valuable physical evidence as is available at the bomb scene.


• Evidence, when subjected to thorough lab examination, gives information which can lead to development or identification of a suspect & association of suspect with the manufacture & placement of the device.

• The FBI’s Explosives Unit maintains an impressive explosives reference collection.


• It has been described as “perhaps the most complete collection in existence of bits & pieces that might be used in an explosive device.”

• Included are actual samples of domestic & foreign batteries, detonators, various blasting accessories, road flares, timers, radio-control devices & components, etc.


• Manuals & catalogues allow technicians to identify a particular type of pipe or other possible component of a bomb.

• The unit also has a computerized bomb reference file that enables experts to link components & techniques with cases having similar characteristics.


• When debris from bomb scene arrives at crime lab, the first step is microscopic examination performed primarily to locate particles of explosive that have not been consumed.

• Chemical & instrumental tests discussed earlier are performed. One device that is sometimes used to screen evidence is called an “explosives detector”.


• The most widely used is the Vapor Trace Analyzer (VTA), a special-purpose gas chromatograph that offers both high sensitivity & high selectivity for particular explosive compounds.

• When sufficient quantities of explosives are recovered, the identifications may be confirmed either by x-ray diffraction or infrared spectrophotometry.


• Infrared spectrophotometry produces a distinctive “fingerprint” patter for organic substances.

• X-ray diffraction gives a characteristic diffraction pattern for inorganic explosives.

• Case study: The World Trade Center Bombing (1993). Watch video.

chemistry. chemistry is 1 of the 5 major science classifications with others being biology, physics,...

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