Analysis

Identification microscopy (e.g., spermatozoa), comparison microscopy (e.g., hairs and fibers), serological analyses (e.g., conventional ABO grouping or species identification), and biochemical analyses (e.g., phosphoglu-comutase) have played a fundamental role in the investigation of crime for many years and are still used today in some circumstances. However, discovery of the specificity of an individual's DNA profile has considerably enhanced the information that can be provided by a forensic science service for connecting a person to an offense and linking offenses to each other. Although a detailed consideration of current DNA techniques is beyond the scope of this chapter, a general understanding of the terms and techniques will benefit the forensic practitioner.

Except for identical twins, each person's nuclear DNA is unique. An individual's gender and DNA profile may be obtained from any of his or her body fluids or tissues (e.g., blood, semen, and bones). The current technical process employed for DNA profiling is termed short tandem repeat (STR) analysis. STR loci are a class of polymorphic markers consisting of simple repeated sequences of 1-6 base pairs in length. STRs are present throughout the human genome (DNA), occurring, on average, every 6-10 kb along the

THE FORENSIC SCIENCE SERVICE

All sections ol this form must be completen and a copy forwarded to Die laboratory Plea» print In capitals using ball-point pen and tick the appropriate boxes.

INFORMATION FORM far the examination of Complainant Use for submission with sexual offences samples (1 per person)

GENERAL INFORMATION

FME

case reference:

Name ol Medical Examiner

Contact telephone number:

Name of Subject

1 Age ] Sex

« I I

f

I Weight I

Dates time of incident

Date & time of examination:

(PWase us« 24 taurclocW

Date & time of other retBvant sexual activity within previous 10 days.

items used in previous intercourse. | Sheath

I I

Spermicide | | Lubricant

Other (Specify)

SPECIFIC INFORMATION RELATING TO THE ALLEGED OFFENCE

Penile/Oral penetration

I No I

I Yes

Penile/Vaginal penetration

IN. ]

I Yes

Penile/Anal penetration

I No I

I Yes

Object penetration

I No I

I Yes

(specify)

Ejaculation onto skin/hair

I NO I

I Yes

(site)

Kissed /licked /bitten (circle relevant action)

I No I

I Yes

(site)

Condom / lubricant /spermicide used

No I

I Yes

(specify)

Menstrual bleeding

I No I

I Yes

Bleeding due to genital/anal injury

I No I

I Yes

(spealy)

THe following removed / inserted:

I Pad

I I Tampon

I I Sponge I I Diaphragm |

Other relevant injuries

I No I

I Yes

(specify)

Showered/washed/bathed/douched

I No I

I Yes

(specify)

Genital/anal/relevant skin area wiped

I No I

I Yes

(how)

Anal intercourse: defaecated since offence

I Ne I

I Yes

Oral intercourse: mouth cleansed since ofience

I No I

I Yes

I Drink

I ( Mouth wash | I Toothbrush !

TOXICOLOGY INFORMATION

Was alcohol consumed?

I No I

I Yes

|Not known I

It Yes please specify

I prior I

I during

I [after [ offence

Start time of drinking:

End time ol drinking:

Quantity and type of alcoholic beverage consumed;

If known, please specify the time of previous urination (I.e. time of urination prior to the specimen provided in this examination)

Date:

Time:

Have any drugs (prescribed or otherwise) been use

by/administered to the subject within 4 days of the examination?

¡No | ¡Yes | ¡Not known |

Yes please specify

prior | ¡during | | after j offence

Give details:

Are other substances suspected of having been used/administered, which could be

elevant to the offence?

¡No I |Ves I ¡Not known j tf Yes please specify

prior | | during | [after | offence

Give details:

FURTHER INFORMATION (Continue on MEDX1C if necessary)

Signature of Medical Examiner

| Date

© The Forensic Science Service, the Association of Police Surgeons and the Association of Chief Police Officers. 2000.

Fig. 2. Proforma used to relay relevant information to forensic scientist. (Reproduced with permission of the members of the Joint Working Party [A.C.P.O., A.P.S., F.S.S., and M.P.S.] for the design of an examination kit for sexual offenses).

DNA and may exhibit a high degree of length variation resulting from differences in the number of repeat units displayed by individuals. Their abundance and hypervariability make them ideal markers for the identification of an individual. When a DNA STR analysis is performed, the specific areas of interest on the molecule are initially targeted. Multiple copies of these areas are then produced using polymerase chain reaction (PCR) techniques, which amplify minute amounts of DNA. The DNA pieces are then sorted according to their size, producing the individual's DNA STR profile (12).

DNA STR analysis, including a DNA sex test (13), is now part of the routine forensic assessment of biological samples in Europe and is replacing both traditional serological analysis of blood groups and classical single-and multi-locus DNA fingerprinting (12). The formation of the European DNA Profiling Group has led to standardization of DNA analysis procedures used in the European community and associated western European countries. The current standard system focuses on analysis of 10 STR loci and is known as AMPflSTR® SGMPlus™. This system contains all of the Interpol and European Networks Forensic Science International (ENFSI)-recommended European loci, which provides points of comparison for DNA intelligence purposes outside of the United Kingdom (14-21). When DNA profiling was first applied to forensic science, large amounts of nucleated material were required. However, the use of PCR technology has enabled much smaller amounts of material to be analyzed. Furthermore, when there are only small amounts of DNA, a technique termed low copy number (LCN) may be used to obtain an STR profile. LCN is a handcrafted, highly sensitive extension of the AMPflSTR® SGMPlus™ that has led to an increase in the sample types suitable for DNA testing, which, in turn, can provide valuable intelligence to the police (22). Because DNA is physically much more resistant to degradation than proteins, it is even possible to analyze degraded samples (23).

Fluorescence in situ hybridization (FISH) is a new technology that uses a Y-specific DNA probe to label male epithelial cells. Once identified, the cells may be separated from the rest of the sample and submitted for DNA profiling. Without separation, the profile may be dominated by the DNA from the examinee, making it difficult to interpret. As yet, it is unclear how useful this tool will be in the forensic setting (see Subheadings 5.1.2.3. and 8.5.2.2.).

Mitochondrial DNA analysis has been used in forensic casework. This technique examines the DNA contained within mitochondria and obviates the need for nuclear material. Because mitochondrial DNA is only passed from mother to child (unlike nuclear DNA, there is no contribution from the father), all the descendants along the maternal line will have the same mito-

chondrial DNA. The technique is best suited to discrete samples, such as hairs without roots and fecal material, and is not ideal for mixtures of body fluids, particularly when the complainant's body fluid is likely to be present in larger quantities than that of the assailant (Tully, G., personal communication, 1998). Therefore, in sexual offenses, the selection of material to be analyzed by this technique is limited and its use needs careful consideration.

The forensic science laboratory must be notified when it is alleged that people who are closely related have been involved in a sexual offense, because their profiles will have greater similarity than profiles from individuals picked at random, and further differentiating tests may need to be performed.

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