Crime Scenes

WHAT IS A CRIME?

• A crime is the commission or omission of any act, which is prohibited or required by the penal code of an organized political state, to which some punishment or sanction is attached.

• Classifications– Felony

• Punishable by death or imprisonment for more than one year in a state prison (ex: murder, rape, terrorism, burglary, treason)

– Misdemeanor• Punishable by fine and/or imprisonment for up to one year in

a local or county jail (ex: petty theft, disorderly conduct, public intoxication, simple assault, vandalism)

– Infraction or Violation• Minor offenses punishable by a fine only (ex: jaywalking, minor

traffic violations, littering, disturbing the peace)

The Six S’s of Crime-Scene Investigation• A lead investigator/first responder starts the

process of evaluating the area.• Securing the scene

– Protect the area within which the crime has occurred• Separating the witnesses

– This avoids witness collusion• Scanning the scene

– primary vs. secondary crime scenes• Seeing the scene

– Photograph and triangulate• Sketching the scene

– Rough sketch of all important objects/evidence• Searching for evidence

– In a grid, linear, quadrant, or spiral pattern

Locard’s Exchange Principle

• With contact between two items, there will always be a transfer of material. The longer or more intense the contact, the greater the amount of trace evidence present.

• “Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and more, bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to find it, study and understand it, can diminish its value.”

Crime Scene: The Beginning• Forensic science begins at the crime scene

• Every forensic investigator has to recognize physical evidence and properly preserve it for laboratory examination

• No amount of sophisticated laboratory instrumentation or technical expertise can salvage the situation if physical evidence is not collected properly

• Crime laboratories “run” on physical evidence• Physical evidence encompasses any and all objects that can

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

• But if physical evidence is to be used effectively for aiding the investigator, its presence first must be recognized at the crime scene.

Types of Physical Evidence• Blood, semen, and

saliva• Documents• Drugs• Explosives• Fibers• Fingerprints• Firearms and

ammunition• Glass• Hair• Impressions• Organs and

physiological fluids

• Paint• Petroleum products• Plastic bags• Plastic, rubber, and

other polymers• Powder residues• Soil and minerals• Tool marks• Vehicle lights• Wood and other

vegetative matter

Categories of Evidence• Class Evidence

Material that connects an individual or a thing to a certain group

• Individual EvidenceEvidence that identifies a particular person

or thing• Trace evidence

Small or microscopic evidence, or evidence in limited amounts

• Direct EvidenceEvidence that provides direct factual

information in a trial • Circumstantial Evidence Indirect evidence used to imply a fact &

incriminate a person• Exculpatory Evidence Helps to prove that an accused is not guilty

Crossing Over

• Crossing over the line from class to individual does not end the discussion.

• How many striations are necessary to individualize a mark to a single tool and no other? – How many color layers individualize a paint chip to a

single car? – How many ridge characteristics individualize a

fingerprint?– How many handwriting characteristics tie a person to

a signature? • These are all questions that defy simple answers

and are the basis of arguments.

Evidence RecoveryPhotography

• The most important prerequisite for photographing a crime scene is for it to be in an unaltered condition.

• Unless there are injured parties involved, objects must not be moved until they have been photographed from all necessary angles.

• As items of physical evidence are discovered, they are photographed to show their position and location relative to the entire scene.

• After these overviews are taken, close-ups should be taken to record the details of the object itself.

–When the size of an item is of significance, a ruler or other measuring scale may be inserted near the object and included in the photograph as a point of reference.

Notes

• Note taking must be a constant activity throughout the processing of the crime scene.

• The notes must identify:– the time an item of physical evidence was discovered– by whom it was discovered– how and by whom it was packaged and marked– the disposition of the item after it was collected

• The note-taker has to keep in mind that this written record may be the only source of information for refreshing one’s memory.

Sketches• Rough Sketch —A draft representation of all essential

information and measurements at a crime scene. This sketch is drawn at the crime scene. It shows all recovered items of physical evidence, as well as other important features of the crime scene

• Finished Sketch —A precise rendering of the crime scene, usually drawn to scale. This type is not normally completed at the crime scene

• Unlike the rough sketch, the finished sketch is drawn with care and concern for aesthetic appearance

Rough sketch vs. Finished sketch

Crime Scene Search Patterns• The search for physical

evidence at a crime scene must be thorough and systematic.

• The search pattern selected will normally depend on the size and locale of the scene and the number of collectors participating in the search.

• Physical evidence can be anything from massive objects to microscopic traces

• There area a variety of crime scene search patterns based upon the type and size of the crime scene.

(a) Spiral

(b) Strip/Line

(c) Grid

(d) Zone/Quadrant

(e) Pie/Wheel

Evidence Recovery Log

• The evidence recovery log is an important document which records all pieces of physical evidence found at a crime scene. This is critical if the case is to be successfully prosecuted later.

The Search continued…• Often, many items of evidence are clearly visible but others

may be detected only through examination at the crime laboratory.

• For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fingernail scrapings, in addition to more discernible items.

• The search for physical evidence must extend beyond the crime scene to the autopsy room

• The medical examiner or coroner will examine the victim to establish a cause and manner of death

• Tissues and organs will be retained for pathological and toxicological examination

• At the same time, arrangements must be made between the examiner and investigator to secure a variety of items that may be obtainable from the body for laboratory examination.

Beyond the Crime Scene

• The following are to be collected and sent to the forensic laboratory:

1. Victim’s clothing2. Fingernail scrapings3. Head and pubic hairs4. Blood (for DNA typing purposes)5. Vaginal, anal, and oral swabs (in sex related

crimes)6. Recovered bullets from the body7. Hand swabs from shooting victims (for gunshot residue analysis)

Packaging Evidence

• Each different item (or similar items) collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

• Each piece of evidence should be packaged properly, sealed in an evidence bag, with the collector’s signature along the taped edge.

• If bag is opened, cut along non-taped edge and reseal and sign when finished.

Obtaining Reference Samples

• Standard/Reference Sample—Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime scene evidence.

• The examination of evidence, whether it is soil, blood, glass, hair, fibers, and so on, often requires comparison with a known standard/reference sample.

• Although most investigators have little difficulty recognizing and collecting relevant crime scene evidence, few seem aware of the necessity and importance of providing the crime lab with a thorough sampling of standard/reference materials.

Evidence in a Court of Law:• Chain of Custody: A list of all persons who came into

possession of an item of evidence.• The chain of custody, if not carefully managed, not only

increases the risk of contamination, but it also can introduce a reasonable doubt

• Frye Standard (1923):• Is the scientific theory/method generally accepted in the

scientific community?• Has the technique been applied correctly?

• Daubert vs. Merril Dow (1993):• Has the scientific theory/technique been tested?• Has the scientific theory/technique been subject to peer

review or publication?• Do standards/controls exist, and are they maintained?• What are the known or potential error rates of the

theory/technique when applied?

Evidence in a Court of Law-Admissibility

• Relevance: does it relate to this particular case

• Material: evidence must relate to the case at hand. Previous criminal records are not material, can be prejudicial and are therefore inadmissible

• Probativeness: evidence must prove something in relation to the case.

• Prejudice: anything that unduly affects the opinion for or against an accused

• Statutory Constraints: also called “privileged information”, or information told to a person who cannot reveal it (clergy, lawyers, etc)

• Hearsay: a statement made outside of court by a person not under oath when the statement was made

Evidence in a Court of Law: Constitutional Constraints

• 4th AmendmentProtects individuals from illegal search and seizure.

Evidence obtained without a warrant, without probably cause, and not listed on a warrant is inadmissible regardless of relevance. (except in the existence of emergency circumstances, need to prevent immediate loss/destruction of evidence, consent of the parties involved)

• 5th AmendmentProtects individuals from double jeopardy and from being

tried for a capital crime unless indicted by a grand jury• 6th Amendment

An individuals right to a speedy and public trial by an impartial jury

• 7th AmendmentCommon law right to a trial by jury

• 8th AmendmentProtection from excessive bail, fines, and cruel and unusual

punishment

Evidence in a Court of Law: Expert Witness

• Forensic evidence relies on the testimony of expert witnesses– A person with the appropriate training and experience

necessary to give valuable information pertaining to evidence used in the trial

• A non-expert is called a lay witness

• An expert must be qualified as an expert every time he/she testifies in court

• An expert is permitted to offer opinions, whereas a lay witness generally cannot

Evidence in a Court of Law

• Innocent until proven guilty…

• Reasonable Doubt: the prosecution has the burden of proof. The defense has the responsibility to either exonerate the accused, or at least introduce a reasonable doubt.– The defense must provide a spirited defense,

regardless of guilt or innocence of the accused (or a mistrial can be called)

• Discovery Motion: the defense is required access to the witness list, as well as other evidence, so that it may carry out its own evaluation of the evidence

Case Studies

O.J. Simpson-1994– Evidence not handled well, leading to suggestions it

was compromised by dishonest criminalists and police.

Outside Nicole Brown-Simpson’s home

JonBenet Patricia Ramsey (1990-1996)

JonBenet Ramsey– Crime scene wasn’t secured and family friends and father found body, contaminating the scene