Forensic Ballistics in Court

Interpretation and Presentation of Firearms Evidence

Brian J. Heard

• Publisher: Wiley
• Year: 2013
• ISBN:
  9781118505014
• Edition: 1
• Topic: Medicine
• Subtopic: Forensic Medicine

Forensic Ballistics in Court: Interpretation and Presentation of Firearms Evidence is an accessible introduction to firearms and ballistics evidence and how this is analysed and presented as evidence in a court of law.

The book approaches the subject in terms of the realities of case work, opening with a clear and illustrated explanation of the correct nomenclature for various weapon types and their parts. Ammunition is also extensively covered, again with annotated illustrations. Basic external and terminal ballistics, wounding capabilities are likewise covered to give an overview of the subject. A key aspect of the book covers the theory and philosophy behind striation matches and the associated statistics, how positive matches should be peer reviewed and the importance accreditation has on this subject.

Gunshot residue formation and identification and the various methods used in its analysis are reviewed in depth. This includes a critical examination of the pros and cons of each type of examination and the evidential weight which can be applied to each method.

• Accessible and reader-friendly introduction to firearms and ballistics.
• Clarifies the limitations of firearms evidence.
• Extensive use of global case-studies throughout.
• Focus on the interpretation and assessment of the weight of firearms/ballistics evidence presented at court.
• Covers the importance of witness and accused statements and their interpretation in relation to the investigation under review.
• Includes coverage of gunshot residue collection, examination and interpretation and the potential for contamination of GSR samples.
• Includes numerous real life case studies that the author has dealt with over the past 45 years.
• Takes an applied approach to the subject.

1.0

Firearms History

1.0.1 Introduction

It may seem that a history of firearms is an illogical way to begin this book, but any competent forensic firearms examiner needs to have a good working knowledge of this subject matter. As such, it should form part of the court qualification process at the beginning of any trial. Having said that, though, it would be unreasonable to expect a firearms examiner with many years' experience to be able to give, for example, a precise date for the introduction of the Anson and Deeley push button fore-end. Such an esoteric piece of firearms history may have formed part of the examiner's training many years ago, but unless s/he had a particular interest in shotgun history it would be unlikely that s/he would remember little other than an approximate date or period.

Knowledge of the subject matter will also add gravitas to the presentation and examination of witnesses by the legal team. It may not help the case, but it will show that the solicitor or barrister is familiar with the history and workings of the presented firearm and can pose knowledgeable questions without the fear of being bamboozled by an expert witness.

It should also be appreciated that there is a very large market in replica ‘antique’ firearms. Some of these are only approximate reproductions of the original weapon, while others are made to the exact measurements of the original. A working knowledge of what these particular weapons look like and how their mechanisms work is therefore a perquisite.

While a history of firearms should start with the earliest of hand cannons, progressing through the wheel lock, miquelet and so on. For this book, however, it will start at the flintlock, as it is unlikely that anything earlier would be encountered in everyday case work. A much more comprehensive history of firearms is offered in Appendix 4.

1.0.2 The Flintlock (Figure 1.0.1)

Figure 1.0.1 The flintlock

The flintlock ignition system really signalled the advent of an easy-to-use firearm with a simple mechanism for the discharge of a missile via a powdered propellant. In this type of weapon, the propellant was ignited via a spark produced by striking a piece of flint against a steel plate. The piece of flint was held in the jaws of a small vice on a pivoted arm, called the cock. This is where the term ‘to cock the hammer’ originated.

The steel, which was called the frizzen, was placed on another pivoting arm opposite the cock, and the pan containing the priming compound was placed directly below the frizzen. When the trigger was pulled, a strong spring swung the cock in an arc so that the flint struck the steel a glancing blow. This glancing blow produced a shower of sparks which dropped into the priming pan, igniting the priming powder. The flash produced by the ignited priming powder travelled through the touch hole, situated at the breech end of the barrel, igniting the main charge in the barrel and thus discharging the weapon.

The flintlock represented a great advance in weapon design. It was cheap, reliable and was not overly susceptible to damp or rainy conditions. Unlike the complicated and expensive wheel lock, this was a weapon that could be issued in large numbers to foot soldiers and cavalry alike.

As in the case with most weapon systems, it is very difficult to pinpoint an exact date for the introduction of the flintlock system. There are indications of it being used in the middle of the 16th century, although its first widespread use cannot be established with acceptable proof until the beginning of the seventeenth century.

Three basic types of flintlock were made:

Snaphaunce (Figure 1.0.2)

Figure 1.0.2 The snaphaunce

A weapon with the mainspring inside the lock plate and a priming pan cover which had to be manually pushed back before firing.

The snaphaunce was used from about 1570 until modern times (in North African guns), but by about 1680 it was out of fashion everywhere except Northern Italy, where it persisted until the 1750s.

Miquelet (Figure 1.0.3)

Figure 1.0.3 The miquelet

A weapon with the mainspring outside of the lock plate, but with a frizzen and priming pan cover all in one piece. In this type of lock mechanism, the pan cover was automatically pushed out of the way as the flint struck the frizzen. The great advantage of this type of lock is that the gunpowder in the priming pan is covered up until the point of ignition by a spring loaded plate, thus allowing the weapon to be used in adverse weather conditions.

It is generally thought that the miquelet was introduced after the disastrous campaign of Algiers (1541), where ‘wind and rain’ prevented firing, firstly by blowing away the gunpowder and/or secondly by wetting the gunpowder. In less than three decades, a lock did appear that is known today as the miquelet lock.

True Flintlock (Figure 1.0.4)

Figure 1.0.4 True flintlock

A weapon with a mainspring on the inside of the lock plate and with the frizzen and priming pan cover in one piece. This also had a half cock safety position, enabling the weapon to be safely carried with the barrel loaded and the priming pan primed with powder. This system was probably invented by Mann Le Bourgeoys, a gun maker for Louis XIII of France, in about 1615.

1.0.3 The Percussion System (Figure 1.0.5)

Figure 1.0.5 The percussion lock

The flintlock continued to be used for almost 200 years. It was not until 1807 that a Scottish minister, Alexander John Forsyth, revolutionised the ignition of gunpowder by using a highly sensitive compound which exploded on being struck. When struck by a hammer, the compound, mercury fulminate, produced a flash which was strong enough to ignite the main charge of powder in the barrel. A separate sparking system and priming powder was now no longer required. With this invention, the basis for the self-contained cartridge was laid down and a whole new field of possibilities opened up.

Once this type of ignition, known as percussion priming, had been invented, it was still some time before ways for it to be applied practically were perfected.

From 1807 to 1814, a wide range of systems were invented for the application of the percussion priming system, including the Forsyth scent bottle, pill locks, tube locks and the Pauly primer cap.

The final form of the percussion cap was claimed by a large number of inventors. It is, however, probably attributable to Joshua Shaw, an Anglo-American living in Philadelphia in 1814. Shaw employed a small iron cup, into which was placed a small quantity of mercury fulminate. This was placed over a small tube, called a nipple, projecting from the breech end of the barrel. When the hammer struck the cap, this detonated the mercury fulminate, causing a strong flame to travel down the nipple and thus igniting the main charge in the breech end of the barrel.

1.0.4 The Pinfire System (Figure 1.0.6)

Figure 1.0.6 The pinfire

Introduced in the United Kingdom at the Great Exhibition in London in 1851 by Lefaucheux, the pinfire was one of the earliest true breech-loading weapons, using a self-contained cartridge in which the propellant, primer and missile were all held together in a brass case.

In this system, the percussion cup was inside the cartridge case, while a pin, which rested on the open end of the percussion cup, protruded through the side of the cartridge case. Striking the pin with the weapon's hammer drove the pin into the priming cup, causing the mercury fulminate to detonate and so ignite the main charge of propellant powder. The pin, which protruded through a slot in the side of the weapons chamber, not only served to locate the round in the correct position, but also aided the extraction of the fired cartridge case.

The pinfire was at its most popular between 1890 and 1910 and was still readily available in Europe until 1940. It had, however, fallen out of favour in England by 1914 and was virtually unobtainable by 1935. Boxes of old ammunition can, however, still be purchased in shooting quantities, from specialised ammunition dealers. This could place into question the placing of this type of weapon into the category of ‘Antique’ rather than that of a firearm requiring certification.

Calibres available for pinfire revolvers were 5, 7, 9, 12 and 15 mm, while shotgun and rifle ammunition in 9 mm and 12 bore and other various calibres were also available.

The really great advance of the pinfire system was, however, not just the concept of it being a self contained cartridge, but obturation, the ability of...