Forensic Science and Law Unit 2

 

WELCOME TO “FORENSIC SCIENCE”” SCIENCE

SHASHANK SHEKHAR TIWARI SENIOR RESEARCH FELLOW SCHOOL OF FORENSIC SCIENCE PhD/FS/RA/004

 

IDENTIFICATION All forensic science, applications, scope relies on identification. • Identification of victim, • Identification of tool or weapon of crime and, • Identification of perpetrator 

 

TYPES OF EVIDENCE Testimonial: Eyewitness accounts accou nts of a crime. Physical evidence: Any material items that are present at the crime scene or on the victims. Trace evidence: Physical evidence that is found at a crime scene in small but measurable amounts.

 

PHYSICAL EVIDENCE (1) It would be impossible to list all the objects that could conc conceivably eivably be of importance importance to a crime. (2) Almost anything can be Physical Evidence. (3) Although Although you cannot rely on a list of categories, it is u useful seful to discuss some of the most common types of physical evidence. (4) The purpose of recognizing physical evidence is so that it can be collected and analyzed. (5) It is difficult to ascertain the weight a given piece of evidence will have in a case as ultimately the weight will be decided by a jury jury..

 

TYPES OF PHYSICAL EVIDENCE • Blood, semen, and saliva • Documents • Drugs • Explosives • Fibers • Fingerprints • Firearms and ammunition • Glass • Hair

• Organs and physiological fluids • Paint • Petroleum products • Plastic bags • Plastic, rubber and other  polymers • Powder residues • Soil and minerals • Tool marks • Vehicle lights • Wood

Impressions  

CLASSIFYING CHARACTERIST CHARACTERISTICS ICS (a) Indivi Individua duall Chara Characte cteris ristic tics: s: Evidence that can be associated to a common source with an extremely high degree of probability is said to possess individual characteristics. In all cases, it is not possible to state with mathematical exactness the probability that the specimens are of common origin. It can only be concluded that this probability is so high as to defy mathematical calculations or human comprehension. Example: Comparison of handwriting characteristics.

 

Characteristics:  (b) Class Characteristics:  Evidence associated only with a group is said to have class characteristics.  

(c) Class Evidence: • One of the current weaknesses of forensic science is the inability of the examiner to assign exact or even approximate probability values to the comparison of most class physical evidence. • For example, what is the probability that a nylon fiber originated from a particular sweater, or that a paint chip came from a suspect car in a hit and run? •and There very few statistical available which this information, in aare mass-produced world, data gathering this from kind of datato is derive increasingly elusive. • One of the primary endeavors of forensic scientists must be to create and update statistical databases for evaluating the significance of class physical evidence.

 

CRIME SCENE INVESTIGATION (CSI)

 

WHAT IS CRIME SCENE  

 A place wher wheree crime occurred. occurred.

• Primary or Secondary? • Mobile or Stationary? • Indoor or Outdoor or Conveyance? • Spread or confined?

 

INDOOR OR OUTDOOR CRIME SCENE Indoor Crime Scene

Outdoor Crime Scene  

•walls Surrounded and enclosed in 4 and ceiling.

• Open area, grounds, roof etc.

• Limited entry and exit routes

• No defined entry or exit routes

• Immune to environmental conditions • Difficult to identify

• Prone to changes due to extreme environment

 

FIRST RESPONDERS • Call the emergency (police, ambulance, fire). • Help the wounded. • Take note of people coming in or leaving the scene. • Make initial observations (look, listen, smell). • If possible, keep it off limits from any intruders, bystanders.

 

CSI REQUIRES… 1. Pr Prot otec ecti tion on o off the the sc scen enee

 

a) From Bystanders

 

b) From yourself 

 

c) From external conditions.

 

CSI REQUIRES… 2. Documentation

a) Notes  b) Sketching c) Photography d) Videography

 

SKETCHING

 

SKETCHING

 

SKETCHING

 

SKETCHING

 

CRIME SCENE PHOTOGRAPHY • Bird Eyes View • Mid Range Photography

• Close-Up Photography

 

CSI REQUIRES… 3. Search

  a) Zonal   b) Linear/Parallel   c) Grid   d) Spiral

 

PRESERVATION & PACKAGING OF EVIDENCES

 

REQUIR REQ UIREME EMENT NT FOR PR PRESE ESER RVATIO TION N •

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Evidence must be preserved in its its original condition condition and must be allowed allowed for changes that take place during analysis and natural degradation with time. Wrongly Wrongl y preserved evidences may m ay be declared unfit for analysis by forensic analysts. Court must be assured that the evidence is authentic. If the sample is allowed to spoil, it may lose key identification characteristics. There may not be enough left for analysis by the forensic expert.

 

EVIDENCE COLLECTION REQUIREMENTS •

Proper Protection of evidence:

  The crime laboratory can only analyze what it receives. •

Sample Sufficiency:

  Insufficient samples are collected by investigators due to lack of proper training. •

Known samples (Exemplars):

The criminal investigators should collect enough samples to satisfy forensic examiners. (signatures, controlled soil sample, test firing etc.)

 

CHAIN OF CUSTODY It can be divided into two parts: 

a) Evidence under custody

  b) Documentaon a) Ev Evid idenc ence e und under er Cust Custody ody::  

- Labelling of evidence while collecng by IO.

 

- Proper packaging and transportaon of evidence.

 

- Laboratory assigns its own serial no. and labelling to evidences.

 

- Serial nos. and inials on each part of evidence.

 

- Aer analysis, evidence must be re-sealed in a tamper-evident manner. manner.

 

- Resealed evidence must be safely transported to the storage.

 

Hazard labelling.

 

b) Documentation:   - Chain of custody documents accompanies the evidence.   - Includes places for sign and date to signify possession of evidence.   - Any official official can instantly identify the possession.   - A property property clerk at the reception area receives the evidence ev idence and case documents, prepare a new file with sign and details of the person that brought the evidence and then forwards it to the labs for analysis.

 laboratory. - This process is similarly similarly followed between different different divi divisions sions with the   - Some laboratories use different different COC COC papers at each level of possession.   - Now-a-days, the evidence evidence packages come with COC paper attached to it. it.

 

COLLECTION TECHNIQUES •

Hand Picking:

  Collection of gross and macroscopic items.   Advantage of establishing the position of material and no further search is required. •

Swabbing:

  Dry swab for collecting collecting minute minute particles.   Wet swab for dried out items especially dried out bodily fluids.

 

COLLECTION TECHNIQUES •

Tape Lifting: Lift ing:

  Use of adhesive tape of not more than 7.5cm in length.   Microscopic materials from garments and motor vehicles especially. especially.   Then transferred transferred to glass or rigid plastic and packed. •

Sweeping:

  Inaccessible are with mass material (vehicular accidents).   New paint brush 25mm wide, new dust pans and brooms(plastic). •

Vacuuming:

  Hair, fiber and other microscopic evidence(tr evidence(trace ace evidences) in dust or powdered surface in a vast area.

  Especially use customized stainless steel nozzles.

 

PACKAGING OF EVIDENCES Four things to be kept in mind while Packaging:  a) Quantity- Better to collect in excess.   b) Controls- Necessary to submit control items to rule out any discrepancies.   c) Reference materialmaterial- For comparison comparison reference items should be collected. collected.   d) Labelling- Directly on the item or on the package. Paper as a packaging material: -

Generally used in various sizes as recommended.

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For placement of clothing and biological samples.

Blood and semen stained material must be kept in paper package before putting in  plastic packaging.

 

CONTAMINATION At the scene of Crime 1) Presecured Scenes:   - Contamination increases with the number of people entering the crime scene.   - Amount Amount of potential destruction of evidence at public places are real challenge.   - Search for events before scene was secured.   - Enquire about person entered at the crime scene. 2) Postsecured Scenes:   - If scene is secured by one officer, others may enter from other avenues.   - Can’t protect something that officer fails to identify as scene of crime.

  -O Outdoor utdoor scene scene can can be contaminated by exte external rnal environment.   - Forming a command post to restrict restrict entry and secur securee out door scene with tents if possible.  

CONTAMINATION Equipment Used at Scene Of Crime   - IO must be aware with the fact of contamination due to their equipment.   - As they travel travel from one place to another, another, they can transfer evidences here & there.   - Equipment Equipment must be decontaminated before and after attendance at SOC.   - Disposable Disposable PPE kits must be be used to reduce reduce contamination. contamination.   - A separate decontamination decontamination zone should be established for quick

decontamination of equipment.  

CONTAMINATION At Packaging and Collection   - New containers must be used for collection.   - Evidence containers must be sealed at SOC.   - Ha Handling ndling of biological samples samples especially especially for DNA purpose is critical,   -W Wet et items must be packaged in paper containers containers afte afterr air drying.   - Ite Items ms from different different places must not be kept at one place.

During Transporting Transporting Evidence

  - Some evidences may be temperature sensitive.   - DNA may disintegrate at higher temperatures,

  - In winter season season precautions should be taken so that that evidence does not freeze.   -T To o avoid leakage of evidences they are kept in plastic bags.  

CONTAMINATION During Laboratory Analysis   - Potential area of contamination is at the reception area where evidences are received.   - Area where sample is unsealed is also potential for contamination.   - Decontamination of both these area must be regularly done with 10% bleach solution.

After the Analysis   - Transporting the evidence to storage may also be a potential for contamination and should be taken seriously.

  Paper containers are porous and may leak during transportation.   - Gloves must be used while dealing with such containers.  

ANY QUESTIONS?