. . . with a broken glass bottlenearby; reddish-brown stains on thewalls, a red stain on the carpet andthe bathroom window smashed.What’s been going on – accident orfoul play?

This is the sort of puzzle that couldconfront a crime scene investigator(CSI) from the police force. Crimescene investigators, often referredto as ‘scientific police’, are one partof the forensic team whose skills areessential in modern policeinvestigation. In the fictitious scenejust described, police must determinewhether or not a crime has occurred.

Roger Beckmann

The forensic teammust collect as muchevidence as ispossible from thecrime scene.

The man may have died of naturalcauses, the stains could be from spiltred wine, and a cricket ball may havesmashed the bathroom window weeksago — or even after the death.

To put the pieces together, a teameffort is required. Police officers willinterview neighbours and gatherinformation about the dead person.A doctor, or forensic pathologist, maybe called to examine the body. Thepolice forensic team must look forclues as to what occurred, and try toreconstruct a possible sequence ofevents.

In the bedroom of 10 Main Street, Murrundrongo,a man in his fifties lies dead on the floor next toa bed . . .

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Forensic – science from

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Forensic – science from

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The science of crimeEvery day, many crimes are committedin Australia. To solve these crimeseffectively – so that criminals arebrought to justice – the police need towork very efficiently, using as manytechniques as possible. Science hasbecome an essential tool for themodern police force.

Originally, the word ‘forensic’ meantanything relating to a law court. Buttoday it refers to a whole new subject.Forensics or forensic science meansusing science to solve crime. But whatexactly does a forensic scientist do?

The work of a forensic scientist fallsinto three broad groups: field,laboratory and medical.

Field workers or CSIs attend thescene of a suspected crime, record indetail what is present, and collect asmuch evidence as possible – withoutcontaminating the scene in theprocess. They search for marks left byimplements such as crowbars, knivesor screwdrivers, or impressions fromshoes and vehicle tyres. CSIs alsoinvestigate fires, explosions and illegaldrug laboratories.

The lab-based forensic scientistsbegin their painstaking analysis of

material using the observations,measurements, physical evidenceand photos collected by the CSIs.

They conduct:• chemical analysis of paint, glass,

fibres, accelerants (substancesused to start a fire), explosives(from discharged guns), inks andprinter toners;

• biological analysis, which includesanalysis of DNA, body fluids,fingerprints and swabs;

• document examination, whichinvolves examining hand-writing,handwriting impressions (eg. froma note written on top of a padof paper), machine-generateddocuments, and paper and inktypes; and

• ballistics, which is the study offirearms and ammunition, and theidentification of particular firearmsfrom fired cartridge cases andbullets. Ballistics also involvescalculating the direction anddistance that a bullet travelled.Another type of lab work in some

police forces is toxicology. This meansdetecting and identifying drugs andpoisons, and determining their effectson the body.

The third area of forensic science –medical – is usually beyond the scopeof police teams. Specialists arebrought in as required. Forensicpathologists are most frequently used,but there are also forensic dentists(to identify teeth and bite marks) andforensic psychiatrists. The medicalexperts use their skills to gainevidence about causes of injury anddeath, or about the identity, behaviourand motivation of a criminal.

Occasionally, other specialists maybe used. Botanists may be calledupon to identify pollen types foundon clothing, while engineers may giveadvice on machinery, buildingcollapses or major fires. A recentdevelopment in forensic science isinformation technology, which meansusing knowledge of computers andsoftware. As such, police will oftenlook for information on a suspect orvictim’s computer. New forms of crime– so-called cybercrime – are makinguse of computers as criminal tools, forexample to acquire information illegallyby ‘hacking’.

Searching for evidence thatmay help solve the crime.

Analysis of objects determine if theywere used in a crime.

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Science has become anessential tool for the modernpolice force.

Meanwhile, back at 10 Main Street,the crime scene investigators willthoroughly examine the area where thebody was found. They will take detailednotes and photographs, look forfingerprints, palm prints and soleprints; marks of tools and weapons;marks from shoes; fibres from clothingor material; fragments of paint andglass and body fluids.

Increasingly, CSIs are usingspecialised techniques, on site, to

Four main uses of forensicsIn Australia, the police characterise fourmain uses of forensic investigation.These are:1. To prove an element of an offence, for

example, to identify a substance asan illegal drug.

2. To associate or disassociate asuspect from a crime scene or crimeexhibit (for example, a weapon).

3. To help determine a possible, orprobable, sequence of events.

4. To provide criminal intelligence, whichmeans to give extra information to thepolice that may be used in the future.For example, if illegal drugs areseized, careful analysis shows achemical ‘signature’ which may revealwhat country or illegal laboratoryproduced them. This may help withother investigations.

determine which areas to concentratetheir investigation on. For example,they may use luminol, which detectstraces of blood by reacting with theiron in the haemoglobin moleculesthat are within red blood cells. Luminolglows when it comes into contact withblood. Sometimes it reveals smalltraces of blood that would normallybe invisible.

The presence of blood, however,does not mean it is from a human, oreven that it had anything to do with acrime. After all, people do occasionallycut themselves, which could leavea tiny drop of blood on the carpet.

In the case of the smashed windowat Number 10, the investigatorsdiscovered traces of blood on theshards of glass, but the stains onthe bedroom wall, and the liquid onthe carpet, were not from blood.

Is it like the TVshows?Forensic scientists are quick to pointout that TV dramas about their workare inaccurate.

The most common misconceptionis that most forensic work is involvedwith murders. Instead, it is involvedwith house burglaries, drug offences,fires and vehicle accidents. Secondly,it is not the forensic experts’ job toconfirm what police investigators wouldlike to hear. Forensic science, like anyform of science, involves having anopen mind and being impartial.

The crime scene investigator or thelab scientist cannot afford to hang onto pet theories or preferred suspects.He or she must work to uncover factsthat can be used as evidence. Quiteoften, these facts may serve to ruleout many of the suspects that thepolice have.

Finally, TV dramas tend to roll allforensic work into one person’sresponsibilities. In real life, forensicscientists are specialists. No singleperson possesses all the knowledgeand expertise of every field offorensics. Solving crimes is very muchteamwork, and modern teams arelarge.

Laboratory based forensicemploy a number ofaccurate scientifictechniques.

The cast of CSI (Crime Scene Investigation)

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Increasingly,CSIs are usingspecialisedtechniqueson site.

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Answers from thedead

Pathology is the study of disease,and cause of death. A forensicpathologist specialises in examiningdead bodies to determine how andwhen death occurred.

As well as examining the body, eitheron site or through photos taken at thescene, the forensic pathologist mayalso use x-ray imaging and will usuallyconduct an autopsy or post-mortem.A post-mortem is a careful dissectionof the corpse, which comes from theLatin language meaning after-death.The pathologist will also take samplesof body tissues, like blood, liver orhair, for further analysis.

One of the first tasks with a bodyon site is to establish the time ofdeath. The pathologist starts withtemperature. The normal temperatureinside a human body is 37

oC.

A pathologist will take the temperatureinside the body, as well as thetemperature in the place where thebody was found. The rate at whichbody temperature falls after deathdepends on the external temperature,the clothing worn, the size of the body,and its percentage of fat.

After 12 hours, most dead bodiesare the same temperature as theirsurroundings, therefore other methodsare required for determining the timeof death. There are many gradualchanges that take place after death.These occur in a particular sequence,concluding with total decomposition.Skilled pathologists can usually usethese changes to assess, roughly,when death occurred.

After the dead body has beenexamined at the scene, it is wrappedfor transport. This is done verycarefully because small details — likefragments of skin, hair or blood caughtunder a victim’s fingernails during astruggle — may provide crucial

evidence, linking a suspect to thecrime. The remnants of explosivematerial from a gunshot may also bepresent on the skin, for example, neara bullet hole. Such residues, andthe bullet wound itself, can giveinformation about the type of bulletused, as well as the distance anddirection from which it was fired.

At the autopsy, pathologists startwith carefully looking at the body andits clothing. They then examine theskin — looking for cuts, scratches,stabs, wounds or injection needlemarks — and the nails.

The body found at Number 10 hada long thin scratch on the shin of theright leg, and had been dead for abouteight hours before police arrived in themorning.

Secrets from withinAlthough a body does not always

show marks on the outside, there isoften evidence inside that will berevealed during the autopsy. In ourscenario, the pathologist found theback of the man’s skull cracked,and a pool of blood inside the skull.

Jorja Fox fromCSI, fires a gunto comparemarks on thebullet and shell.

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The corpse may reveal what caused a person’s death.

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An escape of blood from the bloodvessels like this is called ahaemorrhage. This type of internalbleeding can be fatal, as the pressureof the leaked blood damages thebrain.

There are other clues within a bodythat can show up during an autopsy.For example, a large blood clot withina major artery or vein, or even in theheart itself, may be a cause of naturaldeath, which would rule out foul play.

Samples of a person’s stomachcontents can reveal the last foodeaten. Blood analysis will show theexistence of any poisons, illegal drugsor medicines. Urine in the bladder mayalso be analysed.

Analysis of the blood from the bodyfound at 10 Main Street showed a highconcentration of alcohol. Stomachanalysis revealed the remains of redwine and spirits. Also, damage to theliver was a telltale sign that thedeceased had been a heavy drinkerof alcohol.

Print precisionAnalysis of fingerprints is probably themost well known use of forensicscience. Each fingertip has a patternof fine skin ridges that are slightlydifferent for every person — evenidentical twins.

New prints are taken by a laser-scanning procedure, where the handis placed on a flat glass plate, and itsprint is stored and compared to otherprints electronically.

A new form of identification relieson DNA, which carries the geneticinformation of each person. Everyone’sDNA is different (except for identicaltwins). DNA profiling or typing issometimes called DNA fingerprintingbecause it allows police to identifyan individual in the same way asfingerprints do. DNA can be extractedfrom any body fluid (blood, saliva,sweat, nasal mucus etc) or fromfragments of a body (hair roots,torn skin or flesh).

Forensic scientists do not lookat the whole of a person’s DNAsequence, but rather a sub-set — aDNA profile. DNA profiles are a verypowerful means of determiningwhether two or more samples may ormay not have come from the sameperson. If DNA profiles do not match,they came from different people.However, if they do match, there isstill a very slight chance that theymay have come from different people.

DNA is the same in every cell of thebody, and stays the same throughoutlife. As such, DNA profiles taken atdifferent times and places can becompared in order to determinewhether or not they come from thesame person.

DNA analysis does not enablescientists to build up a picture ofa person from their DNA. The onlycharacteristic that the DNA tells us isthe sex of the person. DNA profiling isonly used to compare different DNAsamples, and to determine whether ornot they could be from the sameperson.

Putting it alltogetherIn our investigation of Number 10,blood found on a shard of glass fromthe broken window yielded DNAidentical to the dead man. The scratchon his shin was recent, and probablythe source of the blood on the glass.

The sticky red liquid on the carpetwas found to be port wine, some ofwhich was also found on the brokenbottle. The source of the wall stainscould not be determined, but they werenot caused by blood.

Police interviewed neighboursseparately, and their statementsconfirmed that the man, a heavydrinker, often arrived home late atnight and had difficulty finding (andusing) his keys. Sometimes he eventried to bang down his own door,or else fall asleep in the bushes.

On the night he died, someone hadheard his drunken singing. It wasprobable that he broke the window togain entry to his own house, as it wastoo cold a night to stay outside. Theforensic evidence suggested that,while drunk, he fell onto a metalradiator near his bed and died fromthe blow to his head. The bottle thathe was holding, broke as a result ofhis fall.

A fingerprint is composed of greaseand dried sweat left behind by the tipsof the fingers. The palms of the handalso leave identifiable prints, as do thesoles of the feet.

Fingerprints can be detected on avast range of different surfaces usinga variety of techniques. The policekeep a huge national database ofprints taken from charged criminals.

DNA analysis does not enablescientists to build up a pictureof a person from their DNA.

DNA fingerprinting has become a powerful tool in helping solve crime.

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Everyone has a unique set of fingerprints.

Counting crimeAcross Australia, the following crimeswere recorded in 2000:approximately 227,000 residentialburglaries;

139,094 motor vehicle thefts;15,630 sexual assaults;9 474 armed robberies; and342 murders.

It is important to realise that thesefigures show recorded crime. Manyminor crimes and some serious crimesare not reported to, or discovered, bythe police.To establish the extent of crime in acommunity, figures are often expressedas rates per 100,000 people. Thisshows that in Australia last year therewere just under 2 murders per 100,000people.It’s interesting to compare Australia’smurder rate with other countries:

Brazil 10 per 100,000USA 7 per 100,000Switzerland 3 per 100,000Japan 1 per 100,000

These comparisons may be slightlyinaccurate because of differences in theway crime statistics are collected andused around the world.Even within a country, different areasexperience different crime rates.Therefore, figures can give a misleadingpicture of your likelihood of being avictim of crime. What is clear, however,is that in Australia, violent crime is farless common than theft.

As in all areas of science, evidencefrom forensic investigation does notmean proof. A correlation between twothings does not mean that one causesthe other.

For example, you might observe thatmost people involved in car crasheswear seat belts, but this doesn’t meanthat seat belts cause crashes. Yourobservation is correct, but you cannotuse it as evidence for the cause ofaccidents. You need to make furtherobservations – for example, of peoplein cars who are not involved incrashes.

Pieces of evidence may not alwaysagree. A fibre found at a murder scenemay match a male suspect’s jacket,but other evidence, such as DNA found

The author would like to thank theAustralian Federal Police ForensicServices, in particular Mr Karl Kent, forgenerous assistance with this article.

The perfect crime?There are many examples of unsolvedand undetected crimes, especially fromthe past when forensic techniqueswere less sophisticated. Even today,there are still crimes committed wherethe criminal is not discovered.

More often, however, forensicevidence allows police to link asuspect to a crime without enoughcertainty to convince a court, and sothe suspect is not found guilty. If thereare no other suspects connected tothe crime, the police must look formore evidence – for example, fromlater witnesses.

However, many criminals areunaware of just how readily they canbe linked to a crime by the skilled useof modern forensic techniques. It isalmost impossible to be in a placewithout leaving a trace of yourpresence in the form of a hair,discarded skin cells, clothing fibresor traces of saliva.

Everywhere we go,we leave a telltalesign of our presence.

at the scene, may belong to someoneelse. There are a number ofpossibilities. The suspect may have:• committed the murder;• been present at the crime,

without committing the offence;• been present at the scene

innocently or suspiciously beforethe crime occurred;

• arrived after the crime and left infright; or,

• been nowhere near the scene andhis jacket was used by someoneelse with or without his knowledge.

Therefore, all evidence must betaken together. Very rarely is one pieceof evidence conclusive proof.

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Correlation is not proof

It is almostimpossible tobe in a placewithoutleaving atrace of yourpresence.