Chemistry

Forensics

Physics

Biology

Chemistry

The study of composition, structure, properties, and reactions of a substance which help us identify a suspect.

Table of Contents

2- Biology2.1: Forensic Autopsies2.2: Blood Testing2.3: Biological Fingerprinting

1- Chemistry1.1: Chemiluminescent

Substrates1.2: Latent Print Identification1.3: Scanning Kelvin Probes

3- Physics3.1: Ballistic Fingerprinting3.2: Ballistic Microstamping3.3: Firearm Identification

Biology

The study of the investigation of living matter, or once living matter, in reference to its origin, behaviour, and classification.

Table of Contents

2- Biology2.1: Forensic Autopsies2.2: Blood Testing2.3: Biological Fingerprinting

1- Chemistry1.1: Chemiluminescent Substrates1.2: Latent Print Identification1.3: Scanning Kelvin Probes

3- Physics3.1: Ballistic Fingerprinting3.2: Ballistic Microstamping3.3: Firearm Identification

Physics

The study that comprises of all investigations that deal with motion, force, and dynamics.

Table of Contents

2- Biology2.1: Forensic Autopsies2.2: Blood Testing2.3: Biological Fingerprinting

1- Chemistry1.1: Chemiluminescent Substrates1.2: Latent Print Identification3.2: Scanning Kelvin Probes

3- Physics3.1: Ballistic Fingerprinting3.2: Ballistic Microstamping3.3: Firearm Identification

Chemiluminescent Substrates

• Light emitted due to a chemical reaction where it is an intermediate state; does not last long

• E in Reactants > E in products;The decay of the intermediate state results in the emission of light

• Used during criminalistics as luminols for tracing blood

1.1

1.1

Luminols

• React with oxidizing agent to emit a neon blue colour (lasts 30 seconds)

• Detect trace amounts of blood (even after being cleaned/removed) using H2O2 where Fe2+ (from hemoglobin) becomes a catalyst

• luminol + H2O2 → 3-APA + excess energy → 3-APA + light

• May react with oxygen presentin copper, bleaches, urine

• Latent fingerprints occur when natural secretions of the skin are deposited on a surface through contact; not readily visible

• Chemical reactions (reagents) are used to reveal hidden chemicals in fingerprints and increase visual contrast

• Iodine, like all halogens, is a good oxidizing agent. Oils from skin, which allow the fingerprint to be created in the first place, are the victims of oxidation

• Solid iodine sublimates (solid → gas)when exposed to room temperature

• AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s)

Latent Print Identification

1.2

Latent Print Identification

1.2

Benazir Bhutto

• Medical report released with an open letter on inconclusiveness

• The amount of blood in the area prevented the FBI from a thorough crime scene investigation

• Law enforcement agencies cited Islamist Web sites as saying al-Qaida had claimed responsibility through an unauthorized official

Forensic Autopsies

2.1

• Thorough examination of a corpse• Determines manner and cause of death,

state of person’s health before death, if medical diagnosis was appropriate before death

• Criminal cases do not requireconsent from next of kin;

• Performed by a pathologist

1. View & Grant Procedure: Body photographed; samples of hair, nails taken; body searched using UV light or radiographic image; wounds examined; general description recorded

2. Internal: Incisions are made down the chest, extended to navel; shears are used to open cavity; organs & major blood vessels are removed and examined and weighed

3. Limbs and face not usually examined internally4. Body is reconstituted by sewing after being lined

with cotton wool-like material

2.1

Forensic Autopsies (Procedure)

Blood Testing

• Analysis of sample of blood extracted from crime scene

• Determine composition, organ function, and other biochemical and physiological properties

• Physical analyses include metabolic measures of chemicals usually present in blood

• Cellular analyses include blood typing, blood count, hematocrit, and DNA testing

• Reveal connection to victim, or crime scene• May reveal cause/manner of death of victim

depending on case

2.2

2.2

Blood Testing

2.3

Fingerprinting• Fingerprints are either patent or latent where the ridges of a fingertip are impressed on a surface

• Patent fingerprints are easily revealed; latent ones are harder to pinpoint

• Iodine can only be used for fresh fingerprints

• Other substances are not as effective, such as silver nitrate (AgNO3)

• Scanning Kelvin Probes is a new technology that is non-contact; allows for the retention of all material; they are not currently is use

• SKPs measure the voltage at pre-set intervals on surface where fingerprint may be deposited

• Measurements mapped to produce 3D image• Physical removal of fingerprint does not result

in loss of entire information of fingerprint: inorganic salts in deposit make metal-ion complexes

• Requires very low points/mmfrequency; is very efficient

• Can only be on metallic or electrically-conductive material

2.3

Scanning Kelvin Probes

Benazir Bhutto

• doctors had tried for 35 minutes to resuscitate Ms. Bhutto

• Dr. Mohamed Mussadik said she was clinically dead on arrival

• Apparently, no autopsy was done, because the “police chief prevented it”

• a medico-legal report based on a mandatory post-mortem examination is a must in a murder case

• The cause of death was reported as “Open head injury with depressed skull fracture”

Ballistic Fingerprinting

• Firearm examination that helps pinpoint the firearm used in a crime

• Matches ballistic striae from the bullet with rifled barrel; matches marks on cartridge with marks in chamber and breech

• Every bullet is marked with a specific “fingerprint” from the barrel when shot, therefore allowing for comparisons

• However, barrels may be replaced inexpensively making this type of testing inefficient

3.1

• Aids firearm identification by engraving marking (make, model, and serial number) on firing pin and breech face using laser technology

• When shot, pressure transfers marking to primer and cartridge case

• After tracking to last retail owner, law enforcement cantrack illegal trade in guns

• Low cost, and highly reliable

Ballistic Microstamping

3.2

• Looking at the wound from a bullet usually identifies gun model if polygonal rifling is not used; velocity can also determine type of gun

• Impacts of bullets from slightly different velocities can affect wound, and therefore be identified

• Each model of a gun has a different velocity (easily determined by a distance/time graph) which are logged by law enforcement

Firearm Identification

3.3

3.3

Firearm Identification

Benazir Bhutto

• Was shot in the neck/head, according to different accounts

• Immediately after, suicide bomber detonated his bomb damaging one of the cars in her motorcade

• Witnesses described seeing a sniper in nearby building

References

• NY Times: Bhutto Assassination• Huffington Post: Bhutto Autopsy• CSGV: Microstamping• Foxnews: How Reliable is Ballistic

Fingerprinting• KelvinProveINFO: SKP• Death Online: Autopsy Procedure

Chemistry

Physics

Biology

Forensics