**8. Evaluation**

*Forensic Analysis - Scientific and Medical Techniques and Evidence under the Microscope*

tics. The process is carried out with the aid of an integrated computer [22].

their textual descriptors' width, kind of tool mark, etc.) [23].

detailed, negative impressions of the working surface of the tool [10].

**6.5 Known tool marks test impressions**

and fair interpretation that can be made.

used to create the impression and so forth.

**7. Interpretation**

**6.4 Databases of tool marks**

collected and an analysis unit for the comparison of pairs of tool mark signatures in order to obtain a numerical similarity value representing their identical characteris-

A wide variety of different tool marks are found at the crime scene due to the different shapes and surface where the tool mark is rendered. Bolt cutters, wire cutters or crowbars have been used to break a door in many cases of burglary. These tools can produce marks that appear in various patterns: impressions and striation marks. Therefore, the Netherlands in collaboration with the Dutch Police developed a database for tool marks, known as Tool Mark Imaging System Database (TRAX). The device is designed for collection, restoration and comparing of tool images and

In practice, the investigator of the tool marks produces negative test tool marks using the suspect tool to compare microscopic surface characteristics between known test tool marks and evidence tool marks. It is recognized that the contrast between a suspected tool and a known test marks is always quicker and more effective than casting or even photography techniques [24]. It is also suggested to use known test tool marks developed in the very same way as the actual tool marks questioned. Traditionally, test tool marks are generated on sheets of soft metal or metal alloy, bars or tubes such as lead, wood alloy and, more recently, lead tape. Firstly, without losing the working surface of the tool, these surfaces are flexible enough to allow test casts with the finest tools. Second, their malleable nature enables the reproduction of the fine scrapes and ridges present on the instrument's working surface in the case of striation marks. Finally, the resulting known test tool marks are accurate, highly

Impressions retrieved from crime scene are compared with reference tools to identify the impressions and to determine if they share a common origin. If there is a good fit between the two impressions, it is necessary to categorize the attributes and explain the probability of it being made randomly or on purpose. In the instance of a negative match between features, a careful investigation is required to determine whether the differences are significant or not and if there is a sensible

The forensic examiners can build a complete probative importance of the decision based on such similar and non-similar findings in order to present it as substantial court evidence. This also demonstrates the examiner's extensive knowledge in explaining and analyzing the fabrication process as well as the tool's wear and tear over time. The following concerns will arise while an expert is doing a mark comparison.

1.Mark the Class and individual characteristic such as substrate and pressure

2.Determine the number and characteristics of the impression present on the questioned tool as well as whether or not you would anticipate to see them reproduced in an impression and how well they relate (or do not) to tool attributes.

**96**

Evaluation is the framework of a conclusive judgment based on analysis and interpretation in significant detail by weighing what the findings mean in reference to the prosecution and the defense statements. There are (at least) three perspectives about how investigators can report their conclusions.

	- The examiner starts by comparing the objects (tools) to see if there are any significant differences that rule out the possibility of a common source. When identifying characteristics are noted, the investigator decides that the items do not share a common source, a process known as "exclusion."
	- When the objects cannot be differentiated (i.e., the likelihood of a common source cannot be ruled out), the examiner then evaluates the rarity or uniqueness of the shared features as a second step. If the examiner believes that the shared features are so unique that they are peculiar (one-of-a-kind), the examiner may infer (and report) that the items are all from the same source—this conclusion is often called individualization or identification. If the examiner believes the shared characteristics are not identical, he or she could state the uniqueness of the related features or the probability that a random tool of the same kind will have them. Similarly, the examiner may claim unequivocally that the artifacts are indistinguishable or that they "play," without mentioning the match's rarity. Eventually, the analyst may conclude the comparison inconclusive.

Additionally, after these two requirements are accomplished, evaluative reports that can be used in court should be generated [25, 26]:


In court, the results of forensic examinations should be evaluated using a probability ratio relying on the findings, associated data and expert knowledge, casespecific propositions and conditioning information. Since the value of the results is dependent on the case information and propositions, this should be emphasized in the report.

The forensic expert opinion should be carried out on the basis of four precepts first stated in an AFSP paper [27]:


To be these above things, experts need to make it express exactly what they have done and with what technique, what highlights have been thought of and why, what grants have been made and why and, last and most importantly, by unmistakably spreading out an indictment and a defense viewpoint upon which to consider the outcomes. These perspectives will without a doubt be restricting and, in instrument mark assessments, as a rule address the expected wellspring of the mark(s). The indictment view that "the submitted tool made the scene mark" is not hard to define [28].
