THE USE OF DNA TECHNOLOGY IN CRIMINAL INVESTIGATION IN TANZANIA.(SAMPLE MANAGEMENT)

BY B JUMANNEFORENSIC DNA UNIT

GOVERNMENT CHEMIST LABORATORY AGENCY

Applications of DNA technology

In criminal investigations scientists utilize DNA profile of a charged person and compare it against DNA (human biological samples) from the crime scene.

For instance; Murder case Rape cases Paternity cases Mass disaster – plane crash, fire accidents,

massacre,

TYPES OF SAMPLES RECEIVED

Biological samples such as blood, buccal swab, semen, sweat in clothes, hair and saliva are usually received and used to extract/obtained sufficient quantities of DNA.

EVIDENCE SAMPLES AT CRIME SCENE LIKELY TO CONTAIN DNA

S/N Exhibit Place where DNA can be found

Source of DNA

1 Knives, Handles and blades of knives

Sweat,blood & skin

2 A cap Inner lining Sweat, hair, dandruff

3 Spectacles/glasses

Nose bridge & earlobe

Sweat, skin

4 Toothpicks, toothbrush

Edge of toothpicks, depris in toothbrushes

Saliva

Cont..5 Cigarette, cigar pipes Cigarette

butts, cigar pipes’ mouth piece

Saliva

6 Bottle, glass, cans, bowls, cups

Rims and edges of bottles, cans, bowls, cups

Saliva, sweat

7 Stamps, envelopes Saliva on envelope seal

saliva

8 Guns, Handles, trigger and burrel

Sweat & blood

9 Clothes underpants, shirts, trousers, dresses, sheets, socks,

Blood, semen, sweat, dandruff, hair

Cont…10 Foot wear Foot wear,

socksSweat & blood

11 Vehicles Car seats, seat belts, steering wheel, tires, window glass, door knobs, buttons, rear mirrors etc…

Sweat, blood, hair, fingerprints & saliva

12 Body parts Kidney, liver, intestines, bones

Blood & tissues

13 Toilets Toilet bowls, seats and floor

Feaces, urine

Responsibility of crime investigators handling DNA samples;

The investigative officer must accept the responsibility for seeing that the right types of samples are received to the DNA laboratory

Responsibility of crime investigators handling DNA samples …..

The point is that the evidence samples should not be exposed to any possibility of destruction, mishandling, contamination, and any other conceivable catastrophe that can be brought on by human or natural error.

Responsibility of crime investigators handling DNA samples …..

The DNA Scientist has to work with what has been submitted to the Laboratory ad the results will depend on the quality of the sample/evidence submitted.

The investigating officer at the crime scene should observe the following guidelines:

GUIDELINES FOR INVESTIGATING OFFICERS

Careful observation of the crime scene prior to handling any evidence samples must be followed

Store crime scene memory in the form of photographs or drawings

GUIDELINES FOR INVESTIGATING OFFICERS….

Isolate/seal the crime scene using police warning tapes until forensic experts arrive

Collecting of evidence samples should be performed by either qualified personnel (crime scene examiner) or Government Chemist laboratory experts

GUIDELINES FOR INVESTIGATING OFFICERS

Collect all possible evidence (materials) that may link a suspect to a crime scene.

Store gathered information in writing (e.g. note books etc).

Use appropriate sampling kits in collecting DNA evidence samples.

GUIDELINES Cont… Appropriate sampling kits should be

utilized in collecting evidence samples

Safety and occupational health guidelines such as the wearing of gloves, shoes and masks should be observed

Collect all the possible evidence (materials) that may link a suspect to a crime scene

GUIDELINES Cont…

Usually blood or buccal swab samples are taken from the suspected perpetrators so as to perform DNA analysis test for profile matching to crime scene samples

Storage and securing of evidence samples;

Evidence samples should be stored according to the case file

Evidence samples should be stored separately and appropriately labeled to avoid contamination of samples

Evidence samples should then be locked away in a secured room

Storage and securing of evidence samples cont…..

Buccal swab evidence samples should be dried out and stored at room temperature whilst raw blood evidence samples should be refrigerated. This is crucial as DNA samples last for an indefinite period of time when preserved properly.

Handling of Raw blood (5-10mls);

A white sterile cotton cloth should be used to soak-up the splattered blood at the crime scene. This cloth should then be air dried and placed in a clean paper envelope.

Blood samples should be packaged in a sterile dry glass bottle mixed with anticoagulant such as sodium fluoride.

Handling of Dried Blood;

Scrap off the dried out blood using a clean scalpel and transfer it to a clean paper envelope.

Alternatively, a white sterile cloth moistened with distilled water can be used to wipe off the dried blood and then air dried and stored in a clean paper envelope.

Packaging and labeling of evidence samples;

Evidence samples must be out of harm's way

The type of evidence samples must be indicated

There should not be more than one label

Permanent (water insoluble) marker pens should be used in labeling samples

Transportation of DNA evidence samples to DNA profiling laboratories;

DNA evidence samples have to be properly sealed/ packaged and labeled so as to prevent them from being tempered with.

The DNA samples must be accompanied with appropriate authoritative forms (e.g., PF 180)

Information which should accompany the samples

The type and amount of evidence samples

The origin of the sample The type of crime committed The type of testing requested The name and signature of the head

of investigation

Information which should accompany the samples cont…

The name of the deliverer of the samples

DNA samples for parentage identification must have referrals from court orders, registered advocates, Police or Social welfare officers.

Conditions under which evidence samples are rejected by DNA laboratories include;

Missing labels on evidence samples Absence of authoritative forms, PF180,

permitting the legal handling of evidence samples

Unlabelled or destroyed labels on evidence samples

Evidence samples not listed in the. PF. 180.

Plastic packaging of evidence samples is not allowed as this may cause degradation of the biological material of interest

Conditions under which evidence samples are rejected by DNA laboratories include;

Dirty packaging of evidence samples

Unpreserved evidence samples More than one label (single

labeling scheme) on evidence samples

DNA Analysis Reports released2005/2006

Types of cases

No. of samples analyzed

Inclusive (%)

Exclusive (%)

Paternity 250 40 60

Murder 159 73 27

Rape 59 UNDER PROCESS

UNDER PROCESS

DNA Analysis Reports released2005/2006 cont…

No. of samples analyzed

Male Female

Sex identification

3 2 1

FACTORS WHICH MAY AFFECT DNA EVIDENCE

Cross contamination while handling evidence samples; Not wearing appropriate attires – e.g.,

gloves Stepping on blood at the crime scene Washing down of evidence located on

toilets or hand wash basins – rape cases

FACTORS WHICH MAY AFFECT DNA EVIDENCE

- Spitting, blowing nose, leaving cigarette buts or smoking at the crime scene.

CONCLUDING REMARKS

Crime scene investigators should possess the necessary knowledge on collection, packaging and transportation of DNA evidence samples.

Confidentiality of DNA evidence samples should be adhered.

THANK YOU FOR YOUR TIME.