The Crime SceneThe Crime Scene

Chapter 2Chapter 2

Physical EvidencePhysical Evidence Physical evidence is any object that can Physical evidence is any object that can

establish that a crime has been committed or establish that a crime has been committed or can link a crime and its victim or its can link a crime and its victim or its perpetrator.perpetrator.

Forensic science begins at the crime scene. Forensic science begins at the crime scene. The investigator must recognize physical The investigator must recognize physical evidence & properly preserve it for laboratory evidence & properly preserve it for laboratory examination.examination.

The evidence must be kept in its original The evidence must be kept in its original condition as much as possible.condition as much as possible.

Securing the Crime SceneSecuring the Crime Scene Secure & Isolate the Crime SceneSecure & Isolate the Crime Scene

First priority is medical assistance to individuals & First priority is medical assistance to individuals & arresting the perpetrator.arresting the perpetrator.

Ropes or barricades and guards will prevent Ropes or barricades and guards will prevent unauthorized access to the area. unauthorized access to the area.

Every person who enters the crime scene has the Every person who enters the crime scene has the potential to destroy physical evidence.potential to destroy physical evidence.

The lead investigator evaluates the scene & The lead investigator evaluates the scene & determines the boundaries. They do an initial determines the boundaries. They do an initial walk through & develop a strategy.walk through & develop a strategy.

All items must be documented & photographed.All items must be documented & photographed.

Recording the Crime Recording the Crime SceneScene

3 methods of 3 methods of crime-scene crime-scene recording: recording: photography, photography, sketches, & notessketches, & notes

Ideally all 3 Ideally all 3 should be usedshould be used

PhotographyPhotography The crime scene should be unaltered, unless The crime scene should be unaltered, unless

injured people are involved, objects must not injured people are involved, objects must not be moved until they have been photographed be moved until they have been photographed from all necessary angles.from all necessary angles. If things are removed, added, or positions If things are removed, added, or positions

changed the photographs may not be admissible changed the photographs may not be admissible evidence.evidence.

Photograph completelyPhotograph completely Area where crime took place & adjacent areasArea where crime took place & adjacent areas Various anglesVarious angles

PhotographyPhotography If crime scene includes a body:If crime scene includes a body:

Take photos to show body’s location & position relative to Take photos to show body’s location & position relative to the whole crime scenethe whole crime scene

Take close-up photos of injuries & weapons lying near Take close-up photos of injuries & weapons lying near the bodythe body

After the body is removed, photograph the surface After the body is removed, photograph the surface underneath.underneath.

When size is significant, use a ruler or other When size is significant, use a ruler or other measuring scalemeasuring scale

Digital cameras allow for enhancement & Digital cameras allow for enhancement & examination in fine detail.examination in fine detail.

Videotaping a scene is also becoming popular.Videotaping a scene is also becoming popular.

SketchesSketches Once photos are taken, sketch the scene.Once photos are taken, sketch the scene. A rough sketch is a sketch, drawn at the crime A rough sketch is a sketch, drawn at the crime

scene, that contains an accurate depiction of the scene, that contains an accurate depiction of the dimensions of the scene & shows the location of all dimensions of the scene & shows the location of all objects having a bearing on the case.objects having a bearing on the case. All measurements are made with a tape measureAll measurements are made with a tape measure Show all items of physical evidenceShow all items of physical evidence Assign each item a number or letter and list it in the Assign each item a number or letter and list it in the

legendlegend Show a compass heading designating northShow a compass heading designating north

A finished sketch is a precise rendering of the crime A finished sketch is a precise rendering of the crime scene, usually drawn to scale.scene, usually drawn to scale. Computer-aided drafting (CAD) has become the standard.Computer-aided drafting (CAD) has become the standard.

Rough-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com.

Finished-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com.

NotesNotes Note taking must be a constant activity Note taking must be a constant activity

throughout the processing of the crime throughout the processing of the crime scene.scene.

The notes may be the only source of The notes may be the only source of information to refresh memory.information to refresh memory.

Tape-recording notes at a scene can be Tape-recording notes at a scene can be advantageous – detailed notes can be taped advantageous – detailed notes can be taped much faster than they can be written. much faster than they can be written.

Dealing with Physical EvidenceDealing with Physical Evidence Once found, physical evidence must be Once found, physical evidence must be

collected & stored in a way that preserves its collected & stored in a way that preserves its integrity for forensic comparison & analysis.integrity for forensic comparison & analysis.

The search for physical evidence must be The search for physical evidence must be thorough and systematic, even when thorough and systematic, even when suspects are immediately seized.suspects are immediately seized.

A forensic scientist is not usually needed at A forensic scientist is not usually needed at the scene unless the evidence is complex or the scene unless the evidence is complex or it is a major crime.it is a major crime.

Some police agencies have trained field Some police agencies have trained field evidence technicians.evidence technicians.

Searching the Crime SceneSearching the Crime Scene One person should supervise & coordinate.One person should supervise & coordinate. Include all probable entry & exit points in Include all probable entry & exit points in

searchsearch What to search for will be determined by the What to search for will be determined by the

particular circumstances of the crime.particular circumstances of the crime. ExamplesExamples

HomicideHomicide Hit-and-runHit-and-run

In most crimes, a search for latent In most crimes, a search for latent fingerprints is required.fingerprints is required.

Systematic SearchSystematic Search

Collect Physical EvidenceCollect Physical Evidence Physical evidence can be anything from massive Physical evidence can be anything from massive

objects to microscopic traces.objects to microscopic traces. It may be necessary to take custody of all clothing It may be necessary to take custody of all clothing

worn by the participants in a crime.worn by the participants in a crime. Handle carefully & wrap separately to avoid loss of trace Handle carefully & wrap separately to avoid loss of trace

evidence.evidence. Critical areas of the crime scene should be Critical areas of the crime scene should be

vacuumed & the sweepings submitted to the lab for vacuumed & the sweepings submitted to the lab for analysis.analysis.

Mobile crime-scene vehicles carry supplies to Mobile crime-scene vehicles carry supplies to protect the crime scene; photo, collect, & package protect the crime scene; photo, collect, & package evidence; & develop latent fingerprints.evidence; & develop latent fingerprints.

Collect Physical EvidenceCollect Physical Evidence The integrity of evidence is best maintained The integrity of evidence is best maintained

when the item is kept in its original condition when the item is kept in its original condition as found at the crime scene.as found at the crime scene.

The entire object should be sent to the lab.The entire object should be sent to the lab. If evidence is found adhering to a large If evidence is found adhering to a large

structure, remove specimen with forceps or structure, remove specimen with forceps or other appropriate tool.other appropriate tool. In the case of a bloodstain, one may either scrape In the case of a bloodstain, one may either scrape

the stain off the surface, transfer the stain to a the stain off the surface, transfer the stain to a moistened swab, or cut out the area of the object moistened swab, or cut out the area of the object containing the stain.containing the stain.

Collect Physical EvidenceCollect Physical Evidence Each different item or similar items collected Each different item or similar items collected

at different locations must be placed in at different locations must be placed in separate containers. separate containers.

Packaging evidence separately prevents Packaging evidence separately prevents damage through contact and prevents cross-damage through contact and prevents cross-contamination.contamination.

Autopsy RoomAutopsy Room Medical examiner or coroner carefully examines the Medical examiner or coroner carefully examines the

victim to establish a cause & manner of death.victim to establish a cause & manner of death. Tissues are retained for pathological & toxicological Tissues are retained for pathological & toxicological

examination.examination. The following are collected & sent to the lab:The following are collected & sent to the lab:

Victim’s clothingVictim’s clothing Fingernail scrapingFingernail scraping Head & pubic hairsHead & pubic hairs Blood (DNA typing)Blood (DNA typing) Vaginal, anal, & oral swabs (in sex-related crimes)Vaginal, anal, & oral swabs (in sex-related crimes) Recovered bullets from the bodyRecovered bullets from the body Hand swabs from shooting victims (for GSR analysis)Hand swabs from shooting victims (for GSR analysis)

Tools for Evidence Tools for Evidence CollectionCollection

ForcepsForceps Unbreakable plastic pill bottles w/ pressure lidsUnbreakable plastic pill bottles w/ pressure lids Manila envelopes, glass vials, pill boxesManila envelopes, glass vials, pill boxes Paper bags are better than plastic…why?Paper bags are better than plastic…why? Fire evidence must be kept in an airtight container Fire evidence must be kept in an airtight container

to prevent evaporation of petroleum residuesto prevent evaporation of petroleum residues Clothing must be air-dried & placed in individual Clothing must be air-dried & placed in individual

paper bags.paper bags. http://www.crime-scene.com/ecpi/evidence_collectiohttp://www.crime-scene.com/ecpi/evidence_collectio

n.shtmln.shtml

Chain of CustodyChain of Custody Chain of custody is a list of all people who came into Chain of custody is a list of all people who came into

possession of an item of evidence.possession of an item of evidence. Chain must be established whenever evidence is Chain must be established whenever evidence is

presented in court as an exhibit.presented in court as an exhibit. Failure to do so may lead to ? Regarding authenticity & Failure to do so may lead to ? Regarding authenticity &

integrity of evidence.integrity of evidence. All items should be carefully packaged and marked All items should be carefully packaged and marked

upon their retrieval at crime sites.upon their retrieval at crime sites. Normally, the collector’s initials & date of collection Normally, the collector’s initials & date of collection

are inscribed directly on the article.are inscribed directly on the article. The evidence container must also be marked with The evidence container must also be marked with

collector’s initials, location of evidence, & date of collector’s initials, location of evidence, & date of collection.collection.

Standard/Reference Standard/Reference SamplesSamples

The examination of evidence often requires The examination of evidence often requires comparison with a known standard/reference comparison with a known standard/reference sample.sample. A standard/reference sample is physical A standard/reference sample is physical

evidence whose origin is known, such as blood or evidence whose origin is known, such as blood or hair from a suspect, that can be compared to hair from a suspect, that can be compared to crime scene evidence.crime scene evidence.

Such materials may be obtained from the Such materials may be obtained from the victim, a suspect, or other known sources.victim, a suspect, or other known sources.

The presence of standard/reference samples The presence of standard/reference samples greatly facilitates the work of the forensic greatly facilitates the work of the forensic scientist.scientist.

Standard/Reference SamplesStandard/Reference Samples Bloodstained evidence must be accompanied by a Bloodstained evidence must be accompanied by a

whole-blood or buccal swab s/r sample obtained whole-blood or buccal swab s/r sample obtained from all relevant crime-scene participants.from all relevant crime-scene participants. A buccal swab is a swab of the inner cheek, performed to A buccal swab is a swab of the inner cheek, performed to

collect cells for use in determining the DNA profile of an collect cells for use in determining the DNA profile of an individual.individual.

Some types of evidence must also be accompanied Some types of evidence must also be accompanied by the collection of substrate controls.by the collection of substrate controls. Normally collected at arson scenes.Normally collected at arson scenes. A substrate control is uncontaminated surface material A substrate control is uncontaminated surface material

close to an area where physical evidence has been close to an area where physical evidence has been deposited; used to ensure that the surface on which a deposited; used to ensure that the surface on which a sample has been deposited does not interfere with sample has been deposited does not interfere with laboratory tests.laboratory tests.

Submitting Evidence to the LabSubmitting Evidence to the Lab Evidence is submitted to the lab either by Evidence is submitted to the lab either by

personal delivery or by mail shipment.personal delivery or by mail shipment. Most labs require that an evidence Most labs require that an evidence

submission form accompany all evidence submission form accompany all evidence submitted.submitted. Enables the lab analyst to make an intelligent & Enables the lab analyst to make an intelligent &

complete examination of the evidence.complete examination of the evidence. Provide a brief description of the case history so Provide a brief description of the case history so

the examiner can analyze in a logical sequence.the examiner can analyze in a logical sequence. The particular kind of examination requested for The particular kind of examination requested for

each type of evidence should be delineated.each type of evidence should be delineated. A list of all items submitted must be included.A list of all items submitted must be included.

Death & AutopsiesDeath & Autopsies Forensic Pathology involves the Forensic Pathology involves the

investigation of unnatural, unexplained, investigation of unnatural, unexplained, or violent deaths.or violent deaths. Forensic pathologists in their role as Forensic pathologists in their role as

medical examiners or coroners are charged medical examiners or coroners are charged with determining cause of death.with determining cause of death.

The forensic pathologist may conduct an The forensic pathologist may conduct an autopsy which is the medical dissection and autopsy which is the medical dissection and examination of a body in order to determine examination of a body in order to determine the cause of death. the cause of death.

Estimating Time of DeathEstimating Time of Death After a human body expires there are several After a human body expires there are several

stages of death.stages of death. Rigor mortisRigor mortis results in the shortening of muscle tissue results in the shortening of muscle tissue

and the stiffening of body parts in the position at death and the stiffening of body parts in the position at death (occurs within the first 24 hours and disappears within 36 (occurs within the first 24 hours and disappears within 36 hours).hours).

Livor mortisLivor mortis results in the settling of blood in areas of the results in the settling of blood in areas of the body closest to the ground (begins immediately on death body closest to the ground (begins immediately on death and continues up to 12 hours).and continues up to 12 hours).

Algor mortisAlgor mortis results in the loss of heat by a body (a results in the loss of heat by a body (a general rule, beginning about an hour after death, the general rule, beginning about an hour after death, the body loses heat by 1 to 1-body loses heat by 1 to 1-1/21/2 degrees Fahrenheit per degrees Fahrenheit per hour until the body reaches the environmental hour until the body reaches the environmental temperature).temperature).

Other SpecialtiesOther Specialties Forensic Anthropology is concerned Forensic Anthropology is concerned

primarily with the identification and primarily with the identification and examination of human skeletal remains.examination of human skeletal remains.

Forensic Entomology is the study of insects Forensic Entomology is the study of insects and their relation to a criminal investigation, and their relation to a criminal investigation, commonly used to estimate the time of commonly used to estimate the time of death.death.

Forensic Psychiatry is an area in which the Forensic Psychiatry is an area in which the relationship between human behavior and relationship between human behavior and legal proceedings is examined.legal proceedings is examined.

Typical blowfly life cycle from egg deposition to adult fly emergence. This cycle is representative of any one of the nearly ninety species of blowflies in North America. Courtesy E. P. Catts, Ph.D., deceased, and Neal H. Haskell, Ph.D., forensic entomology consultant www.forensic-entomology.com.

Other SpecialtiesOther Specialties Forensic Odontology involves using teeth to Forensic Odontology involves using teeth to

provide information about the identification of provide information about the identification of victims when a body is left in an victims when a body is left in an unrecognizable state; also investigates bite unrecognizable state; also investigates bite marks.marks.

Forensic Engineering is concerned with Forensic Engineering is concerned with failure analysis, accident reconstruction, and failure analysis, accident reconstruction, and causes and origins of fires or explosions.causes and origins of fires or explosions.

Forensic Computer Science involves the Forensic Computer Science involves the examination of digital evidence.examination of digital evidence.

Crime Scene SafetyCrime Scene Safety The increasing spread of AIDS and hepatitis B has The increasing spread of AIDS and hepatitis B has

sensitized the law enforcement community to the sensitized the law enforcement community to the potential health hazards that can exist at crime potential health hazards that can exist at crime scenes. scenes.

In reality, law enforcement officers have an In reality, law enforcement officers have an extremely small chance of contracting AIDS or extremely small chance of contracting AIDS or hepatitis at the crime scene.hepatitis at the crime scene.

The International Association for Identification The International Association for Identification Safety Committee has proposed guidelines to Safety Committee has proposed guidelines to protect investigators at crime scenes containing protect investigators at crime scenes containing potentially infectious materials that should be potentially infectious materials that should be adhered to at all times.adhered to at all times.