Forensic Analysis and Interpretation of Tool Marks

*Sachil Kumar, Geetika Saxena and Archana Gautam*

## **Abstract**

The forensic analysis and interpretation of tool marks raise for consideration key methods and advances in the field of tool marks in forensic science. This chapter shows how tool mark analysis can be utilized in the course of criminal investigations. The focus of the chapter is on bringing together as much scientific knowledge in the area as possible in an accessible manner. It covers all aspects of tool mark evidence from the crime scene to the courtroom. This chapter provides information about tool marks in an effort to assist tool mark examiners as well as people practicing forensic science, crime scene examiners, crime investigating officers and members of the legal profession. It includes information about the analysis of tool marks at the crime scene and in the laboratory, the interpretation and assessment of challenges for examination and interpretation and also the way in which tool mark evidence can be presented in a courtroom.

**Keywords:** forensic analysis, tool marks, investigation, court, crime scene, interpretation

### **1. Introduction**

Tool mark identification is a fascinating forensic science discipline. By comparing the pattern of the tool marks in question and the pattern of the tool marks generated by the tool in a laboratory environment, a skilled analyst can give an opinion based on the accuracy of the questioned tool mark produced by a specific item [1]. This assists the forensic investigator in matching the marks on tools to crime scenes. Forensic tool mark identification includes firearms identification, an area of tool mark investigation that specializes in identifying different firearms and parts of a firearm being used at crime scenes. It also includes fracture matching or a physical fit [2], whereby two specific objects are analyzed to determine whether they have been at one time a single unit. If that is the case, the investigator will further analyze how the two objects come into contact and how they affect each other.

Tool marks can be generally understood as impressions or marks that are produced by a tool [3]. When a tool contacts a surface with sufficient force, a mark or an indentation is permanently left on the receptive surface.

A striation, as defined by AFTE, is a range of marks on the surface of an object [4]. These marks are produced by a combination of impact and motion. A pry mark made by the tip of screwdriver is a type of striated tool mark [2]. Similarly, an impression can be defined as a range of marks on the surface of an object [4]. As with a striation, an impression is produced by a mixture of impact and motion. Notably, impressions are not caused by strong impact but appear on a surface as soft or shallow indentations. A hammer impact is a type of impressed tool mark.

Tools may be connected to tool marks and vice versa due to certain patterns or anomalies during the manufacturing process embedded in their surface. It is argued that patterns and anomalies of the tool mark are specific to each tool; the distinguishing features of a particular tool may be one aspect, just as the markings on a bullet can lead to a particular one and can be identified and compared visually. In consideration of this, a forensic investigator can become familiar with the manufacturing processes used to manufacture the working surface [5] of a tool and can compare the class features with the same surface of the tool such that it is possible to measure the uniqueness of a tool and its tool mark. Knowledge and understanding of tool manufacturing methods, along with close examination of tools and markings of tools, will make it easier to carry out this particular recognition.

There was no direct way in the past to associate a tool mark with the tool itself, and little progress has been achieved with the advent of modern forensic technology. In using tools to gain entry, a burglar will invariably leave tool marks behind that are of forensic significance and potentially incriminating, which can provide vital evidence to investigators and prosecutors. Given this, the essential factors that influence both tool mark production and the subsequent inspection of such marks in the forensic examination can be determined. These factors include the following:


#### **2. History of tool marks**

Since many previous centuries, a historical understanding of the tool mark has been recognized that marks can be connected directly to tools, but few written references are typically found on this specific subject. A cited example often comes from China in the Twelfth century, where various wound shapes created by cutting tools such as sickles were considered, but even in China, there is little evidence of their importance.

Henry Goddard (1800–1883) of Scotland Yard is remembered as the first investigating officer to collect forensic evidence by analyzing a bullet and its related pattern to investigate a murder [7]. In 1835, using a bullet recovered from the autopsy victim's body, a defect was discovered that could be traced back to the original mold from which the bullet was made. In 1891, Hans Gross published a book entitled "Handbuch für Untersuchungsrichter als System der Kriminalistik" detailing all the basic precautions for the analysis of tool marks [8].

In 1953, a popular book entitled "Crime Investigation" textbook written by the renowned criminalist, Paul Leland Kirk (May 9th, 1902 – June 5th, 1970), explains the need for cast marks found in crime scenes if the item with the mark cannot be transported to the laboratories and makes a strong distinction between "compression marks" and "sliding marks." In his book, he examined immersed marks by using macrography while comparison microscope was used to analyze striated

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*Forensic Analysis and Interpretation of Tool Marks DOI: http://dx.doi.org/10.5772/intechopen.98251*

bullet surface scanning technology [10].

**3. Definition of tool marks**

being marked.".

for objective methods for evaluating striated marks.

marks, was founded in the United States in 1969 [11].

accused person and the incidence of the crime.

sliding action or cutting action occurring.

**4. Types of tool marks**

marks, along with the examination of physical fit. In the 1974 edition, there is a reference to the work by Biasotti [9], *The Principles of Evidence Evaluation" as applied to Firearms and Tool Mark Identification*, which contains some of the first references

In 1958, a book entitled 'An Introduction to Tool Labels, Weapons and the Striagraph' was written by John E. Davis, a prominent criminalist and the chief of the Oakland Police Department (CA) Criminalistics Division (Crime Lab). This textbook also introduced a new advanced piece of research equipment called "Striagraph," which was able to calculate, trace and record microsurface contours and was the precursor to advanced laser and digital imaging techniques for future

The Association of Firearms and Tool Mark Examiners (AFTE), an international nonprofit organization devoted to facilitating the identification of firearms and tool

Tools are mostly directly related to object markings, because at the time of tool production, such designs or irregularities are imprinted on their surface, so it is implied that these patterns and variations might be part of the identification features of a particular object; for example, marking bullets can lead to a particular firearm. Furthermore, these substantially different types and irregularities of the instrument can be visually identified and compared using forensic techniques [12]. The term "tool mark" is defined in a number of ways. A widely accepted AFTE definition defines tool mark as "If any object or instrument reaches the surface with enough force to allow its signature design to be indented, this form of marking is referred to as a tool mark.". In another definition [6], it is stated that "An instrument that is considered to be sufficiently stronger from two objects acquires comprehensive force when it comes into contact with each other, which leads to the softer one

Biasotti and Murdock [13] state that "When two objects begin to interact, the extremely hard object will stamp the surface of the softer object. The relative hardness of the two artifacts, the pressures and motions, and the appearance of the microscopic discrepancies on the object are all factors influencing the character of the generated toolmarks." It is necessary to establish the correlation between a tool mark and the tool that produced it in criminal investigations such as burglaries. For instance, if a burglar chooses wooden or metal bars to force entrance into a home, the marks left by the tool on the doorway are strong evidence of the involvement of that tool for that legitimate purpose at the scene of the crime. If the tool is linked with, or close to, a suspect, it enables for the identification of a link between the

Generally, there are three categories of tool marks left by tools on the surfaces they hit. These impressions are produced by the possibility of a compression action,

A compression impression: Probably the most common and most negative representation of the surface of the tool, caused by pressure, blow or gouge of the tool on the surface of a wood, metal or other surface. Compression is imprinted on softer material when tool surface presses against its surface [14]. For instance,

*Forensic Analysis and Interpretation of Tool Marks DOI: http://dx.doi.org/10.5772/intechopen.98251*

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

or shallow indentations. A hammer impact is a type of impressed tool mark.

ings of tools, will make it easier to carry out this particular recognition.

4.The manufacturing procedure followed in order to construct the tool

Since many previous centuries, a historical understanding of the tool mark has been recognized that marks can be connected directly to tools, but few written references are typically found on this specific subject. A cited example often comes from China in the Twelfth century, where various wound shapes created by cutting tools such as sickles were considered, but even in China, there is little evidence of

Henry Goddard (1800–1883) of Scotland Yard is remembered as the first investigating officer to collect forensic evidence by analyzing a bullet and its related pattern to investigate a murder [7]. In 1835, using a bullet recovered from the autopsy victim's body, a defect was discovered that could be traced back to the original mold from which the bullet was made. In 1891, Hans Gross published a book entitled "Handbuch für Untersuchungsrichter als System der Kriminalistik" detailing all the

In 1953, a popular book entitled "Crime Investigation" textbook written by the renowned criminalist, Paul Leland Kirk (May 9th, 1902 – June 5th, 1970), explains the need for cast marks found in crime scenes if the item with the mark cannot be transported to the laboratories and makes a strong distinction between "compression marks" and "sliding marks." In his book, he examined immersed marks by using macrography while comparison microscope was used to analyze striated

1.The surface material that the tool is functioning on

2.The material used in order to construct the tool

3.The relative hardness of each material

basic precautions for the analysis of tool marks [8].

5.The tool operational surface [6].

**2. History of tool marks**

their importance.

Notably, impressions are not caused by strong impact but appear on a surface as soft

Tools may be connected to tool marks and vice versa due to certain patterns or anomalies during the manufacturing process embedded in their surface. It is argued that patterns and anomalies of the tool mark are specific to each tool; the distinguishing features of a particular tool may be one aspect, just as the markings on a bullet can lead to a particular one and can be identified and compared visually. In consideration of this, a forensic investigator can become familiar with the manufacturing processes used to manufacture the working surface [5] of a tool and can compare the class features with the same surface of the tool such that it is possible to measure the uniqueness of a tool and its tool mark. Knowledge and understanding of tool manufacturing methods, along with close examination of tools and mark-

There was no direct way in the past to associate a tool mark with the tool itself, and little progress has been achieved with the advent of modern forensic technology. In using tools to gain entry, a burglar will invariably leave tool marks behind that are of forensic significance and potentially incriminating, which can provide vital evidence to investigators and prosecutors. Given this, the essential factors that influence both tool mark production and the subsequent inspection of such marks in the forensic examination can be determined. These factors include the following:

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marks, along with the examination of physical fit. In the 1974 edition, there is a reference to the work by Biasotti [9], *The Principles of Evidence Evaluation" as applied to Firearms and Tool Mark Identification*, which contains some of the first references for objective methods for evaluating striated marks.

In 1958, a book entitled 'An Introduction to Tool Labels, Weapons and the Striagraph' was written by John E. Davis, a prominent criminalist and the chief of the Oakland Police Department (CA) Criminalistics Division (Crime Lab). This textbook also introduced a new advanced piece of research equipment called "Striagraph," which was able to calculate, trace and record microsurface contours and was the precursor to advanced laser and digital imaging techniques for future bullet surface scanning technology [10].

The Association of Firearms and Tool Mark Examiners (AFTE), an international nonprofit organization devoted to facilitating the identification of firearms and tool marks, was founded in the United States in 1969 [11].
