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TOOLMARK EVIDENCE

Tool mark: Impressions left by forcible contact of any implement with a softer surface.

TYPES OF TOO MARK1. Indentation marks: An indentation is caused by tool when it is pressed upon a surface without sliding

motion [static impact]. The mark contains outline of a tool surface with its irregularities. The clarity and

individuality of marks depend on surface of tool, force of impact and nature of recipient surface.

Examples: Hammers, Punches, Dies, Metal stamps and seals, Stones and Bricks etc.

2. Scrap Marks: A scrap marks are caused by sliding contact with receiptant surface. The surface is

scratched with characteristics fashion depending upon irregularities of scratching surface of tool. Scrap

marks are found in form of lines [striations]. The width, depth and inter-distance of scratched lines vary to

certain extent depend upon angle of application.

Examples: Cutting tools such as Sword, Knife, Axes, Scissors, Shovels used to dig earth etc.

3. Saw Marks: It includes hacksaw marks are class by themselves. When the whole length is cut through,

the saw or hacksaw leaves its pattern of the cut surface. It indicates number of teeth per unit length. If

some teeth are broken their number position and shape may allow positive identification of saw marks

4.Drilled Marks: Holes dug by drills and bits in wood are frequently troublesome for identification

purpose. If the holes is not through and through the bottom of the holes carries the carries the

identification of surface of tool.

5. Print Marks: Printing from printing block is identification, as every printing block has on its own

defects of omission and commission.

6. Broken/ Severed Parts: Broken and Severed parts of articles recovered from scene of occurrence and

those from the person, house or vehicle provide a definite type of evidence if hand-in-glove fit is

obtained. Broken and severed articles can be bone, a nail, a tooth, apiece of skin a tool, a glass, a wooden

piece a leaf, board, pipe, ornament magazine or news paper.

7. Contact marks: Articles which are joined together by glue, nails, etc exchange contact marks. It they

are detached, the fact that they were originally attached and can be establishing for purpose of contact

marks.

Documentation/ Recording of Tool Marks.1. Plasticine: They do not pick up fine details and are easily deformed. They are prepared only when they

are not required for permanent record, or when area bearing mark is small. A lump of plasticise is taken

and pressed in between two wet glass plates to give it smooth surface. The moistened area is pressed

against mark.

2. Dental Stone: Dental mass is available with a dental surgeon or chemist selling dental material. It canpick up details and can record mark permanently. The material is kneaded under hot water and when it is

soft and uniform in texture, it is pressed between two glass plates to give smooth surface. The material

while still warm and pliable is pressed against the mark.

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3. Adhesive tapes: Lifts only shallow tool mark impressions.

4. Latex and plastic solution: It good to record scrap marks but not good for indentations as dimensions

of lift marks change during stretching. The material is poured over surface bearing marks and is allowed

to dry for six hours.

5. Woods metal: It is an alloy made up 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by

weight, which melts at low temperature. It is used to indentation marks with appreciable depth. Woods

metal is toxic as it contains lead and cadmium in its composition.

6. Extraneous materials: When traces of extraneous material are found on a tool, it is placed in

cellophane envelop before dispatch. When they are found on scratches, articles is placed in cellophane

envelop. If not possible traces are collected on paper with clean camel hair brush.

EVALUATION OF TOOLMARKS.Principle: Practically and theoretically it is impossible to get two tools which are exactly alike even whenthey are manufactured consecutively in a rigidly controlled manufacturing process with most

sophisticated precision machines.

1. Mechanical Fits: In case of broken parts, mechanical fit is tried first. Positive mechanical fit provideconclusive proof that the parts originally formed part of the whole. The fit is photographed at various

positions to get complete contour picture.

The broken and severed end parts may carry microscopic details on the outer surface, such as

striations, some deposits, some defects, logo etc. The marks are introduced in manufacturing process

or later by wear and tear.

2. Side by Side match: Indentations, punch marks and print marks from blocks, dating and numberingmachines are compared when the disputed and exemplar are placed side by side. The main points of

defects and wear and tear, their sizes and shapes, interdistance are examined and compared to find out

if marks have common source. The examination and comparison is facilitated by a transparent graph

sheets placed over the photograph of two marks taken with same magnification.

3. Composite match: The photographs are taken through comparison microscope. The images of halfof each questioned test marks are adjusted at dividing line. If two halves complete the original mark

without any divergence, identity of common source is established. [Indentations, prints, scrap marks].

The line observed in questioned mark show continuation in test marks only if they have same source.

4. Striagraphy: The instrument striagraph has been developed to study striations on different objects. Adelicate probe moves over the surface being studied. The changes in depth and elevations are

recorded on graph and elevations are recorded on graph paper separately for questioned and test

marks. The instrument does not offer any advantage over comparison microscope.

5. Superimposition: Indentations scrape marks, punch marks and print marks are evaluated by thistechnique but most commonly used for indentation and punch marks.

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Method-1: In photographic superimposition a print prepared from one of marks (say questioned). A

transparency is prepared from test mark. The photograph and transparency have some magnification

or reductions to get corresponding dimensions. Match is studied by placing transparency over

photographic print. Various landmarks should correspond- over lap.

Method-2: In this method, test is: printed on adhesive transparent sheet and covered with clear

plastic sheet. The print is now like transparency. The test mark to show match. If necessary the

contrast is increased by smearing with fingerprint powder.