For MARCH 2003 issue

SCIENCE IN CRIME DETECTION-114

DETECTION AND SIGNIFICANCE OF BLOOD IN FIREARMS

‑Dr. Anil Aggrawal

As the incidence of homicides increases all around the world, especially in our country, one finds firearms of various kinds, especially handguns, being involved with much greater frequency than ever before. In addition to homicides, there are many cases in which individuals are superficially or seriously wounded by firearms, and it is necessary for thorough firearms investigation to be conducted in those cases as well as in all homicides caused by firearms.

This piece deals with an investigative aspect of firearms investigation that unfortunately is not always undertaken in many jurisdictions, namely, the detection and scientific evaluation of blood particles, stains or patterns on alleged weapons. What can the presence of blood on a firearm tell the investigator and to what extent can it assist him in his examination of an alleged murder or assault with a weapon? What techniques and scientific equipment are available and what level of knowledge can appropriate experts bring to bear in this important and frequent area of investigation? Are there patterns that can be detected that can help law enforcement officers and forensic pathologists better understand the manner in which a particular crime occurred? Can these patterns give information concerning angle, range of fire, etc?

The significance of bloodstain evidence is recognized to a much greater extent today than it was some years ago. In fact, prior to a 2 year research project on bloodstain evidence interpretation conducted from 1969 to 1971, very little had been accomplished with evidence of this type. Nevertheless, some mention of the possible evidentiary value of bloodstains was given by the noted Austrian criminologist, Hans Gross, as early as 1893. By 1904 Florence and Fricon, two French researchers, had conducted bloodstain experiments and “had even attempted to deduce the course of a crime from the location and shape of blood spatters.”

In spite of these earlier reports, bloodstain evidence was apparently disregarded for many years. In his second English edition, Gross devoted an entire chapter to “Traces of Blood” and even outlined experiments for producing standard blood patterns. However, that chapter was omitted from the fourth and fifth editions. Apparently, while some of the earlier investigators may well have been familiar with bloodstain patterns, their publishers and/or editors may have decided that such information was of little value and simply deleted it from later publications. During the period 1930 to 1954 no articles appeared that added to an understanding of bloodstain pattern interpretation. However, in 1955 Dr. Paul L. Kirk filed his affidavit on physical evidence in the Sheppard case, much of which dealt with bloodstains. That document expanded the scope of bloodstain evidence interpretation far beyond the earlier work of Gross and was, undoubtedly, the most comprehensive report on the subject for many years. Unfortunately, the existence of Kirk’s affidavit was not general knowledge as it was not well circulated.

Without question, Kirk was the first person in the United States to apply his scientific knowledge to the practical interpretation of bloodstain patterns. He had given testimony on this subject as early as 1956, and this testimony was recognized as being proper when reviewed by a higher court following appeal. That court stated:

Evidence that he had made experiments was introduced to qualify him as an expert in blood dynamics, to show that by training and experience he was able from an analysis of the size and shape of blood spots to determine their source with some degree of accuracy, and to enable the jury to test the reliability of his opinions by revealing their foundation. For these purposes the evidence was properly admitted.

Kirk’s testimony during the second Sheppard trial was also regarded by many as being significant. In fact, the jurors were polled after that trial and “it was reported that they considered Dr. Kirk’s testimony very important and his methods extremely careful.”

More recently, during the past few years, the value of bloodstain evidence has become a subject of much greater interest among both civil and criminal investigators. Undoubtedly, this interest is largely due to two closely related events. First, in November 1971, the Law Enforcement Assistance Administration accepted, had printed, and distributed the report on bloodstain evidence research that had been conducted during the preceding two years. That research had been sponsored by a grant from the National Institute of Law Enforcement and Criminal Justice. As a Government Printing Office document that report received widespread distribution to law enforcement agencies throughout the United States and other countries.

Secondly, a very experienced researcher Herbert Leon MacDonell conducted many experiments on the blood stain spatters. As is often the case, however, while some answers were obtained from research, new questions were also generated. One such question related to the presence of blood in the muzzle of a firearm. This condition had been observed several times while examining weapons in gunshot deaths. Was there any correlation between such stains and discharge distance? That is the question which prompted a very interesting investigation about which I am going to write. This investigation was done by the most famous researcher on blood stains Herbert Leon MacDonell.

OBJECTIVE

The process of this research was fourfold. First, targets had to be prepared that would approximate human heads as closely as possible. Second, a variety of weapons which might likely be encountered were assembled. Third, a method for removing residues from a muzzle and testing for blood traces had to be developed. Fourth, whatever correlations that might exist between the various factors had to be established as accurately as possible.

EXPERIMENT DESIGN

Polystyrene heads normally used to display hair pieces were obtained from a beauty salon supply house. These heads were coronally sectioned using a rip saw to allow a “hollowing out” of a cranial cavity. This was accomplished using a propane torch as shown in Figure 1. The two halves were reassembled using strapping (filament) tape. A 3 x 3 inch panel approximately 0.25 inch depth was removed from the forehead or frontalis region using a soldering gun as a convenient cutting tool. A 0.25x3x3 inch pad of polyurethane was inserted into this void area, which was then covered with a slightly larger sheet of plastic (Saranwrap) secured by transparent tape along its edges. The entire head was given three or four coatings of Liquid Rubber to complete the assembly.

A thick mixture of gelatin was prepared to simulate brain matter for the cranial cavity. After preparation, the mixture was poured into the base of each head through a preexisting tapered hole and allowed to set overnight. The tapered hole is evident in Figure 1.

Final preparation of a head for test firing consisted of injecting 30 ml of whole human blood into the polyurethane pad. This was accomplished by using a hypodermic syringe and injecting blood through the latex covering at a point near the top center of the pad. The pad had to be subjected to alternate compression and relaxation to promote uniform saturation with blood. After the needle was withdrawn, a simple sealing of the injection hole was effected by using transparent tape as a “band aid.” A completed, blood - saturated head ready for test firing is shown in Figure 2. While no effort was made to simulate bone, it was felt that this was not a serious omission. Our results, therefore, show at least as much, if not more, back spatter than would likely result from a shot into an actual human head.

A rather wide variety of firearms was selected. To provide additional scope, several discharge distances were used with each. Only one shot was fired per head. Most of the following were test fired at contact and at 1, 2, and 3 inches from muzzle to target. The following firearms were used.

12-gauge single - barrel shotgun

12 - gauge double - barrel shotgun

16 gauge recoil - operated, autoloading shotgun

20 - gauge recoil - operated, autoloading shotgun

.308 Winchester

.45 ACP

.38 special revolver

.357 magnum revolver

.22 revolver

Some of the above were also fired at 5 inches.

TEST FIRINGS

Test firings were conducted as illustrated in Figure 3. The test head was placed over a large wooden dowel that was secured in a substantial lead clamp weighing 12 lb. Discharge distance was accurately maintained by resting the muzzle end of each test weapon on a large polyurethane pad that was taped to the pan head of an adjustable tripod. A polyethylene bag was placed over this tripod support to prevent staining from backspattered blood. (In fact, in many cases the person discharging a weapon elected to do so while covered with a large polyethylene sheet for the same reason.)

Results of test firing were recorded by both still and motion picture photography. A typical example of the effect of shotgun discharge is shown in Figure 4. Blood may be observed spewing from below the tumbling head in this figure.

It was also necessary to develop a reliable sampling procedure to measure the depth of blood penetration into the muzzles of the various firearms. Several initial methods were evaluated from which it was concluded that a sheath system was necessary for inserting a swab into smaller diameter barrels. With care, a sheath was unnecessary when sampling shotguns. The only difference between sampling handguns and longer weapons was the preparation of swabs. The individual procedures are described below.

Handguns

Depending upon the caliber, one or the other of two sizes of pipe cleaner/ straw combinations was used. Plastic straws are available in 1/4 inch and 5/32 inch diameters. Large (5/16 inch diameter) pipe cleaners may be purchased in continuous lengths from chemical supply houses for cleaning laboratory glassware. This material is used with the larger straws for handguns of .30 caliber and larger. Ordinary pipe cleaners (1/8 inch diameter) are used with the smaller straws for .22 to .30 caliber. Regardless of which combination was used, the following procedure was adopted:

1. A straw is cut about 1 inch longer than the barrel of the weapon. A piece of pipe cleaner is cut about 2 inches longer than the straw (Fig. 5).

2. The pipe cleaner is first saturated with water and then inserted into the straw until it is flush on one end. The flush end is inserted into the barrel of the weapon until it extends about 1/2 inch from both breech and muzzle. If possible, insertion should be made from the breech end. This is not possible with solid - frame revolvers, as is evident in Figure 6. It is important that insertion of the straw be accomplished without scraping the inside of the barrel. Such contact could result in possible contamination further down the barrel and would suggest greater depth of blood penetration. Naturally, this applies only when the straw has been inserted from the muzzle end.

3. The plastic straw is pulled back flush with the breech by holding the pipe cleaner about 1 inch from the muzzle and sliding the straw over the pipe cleaner.

4. The exposed pipe cleaner in the breech is bent over and firmly held while the straw is withdrawn from the muzzle end (Fig. 7).

5. A “crank” is formed by making two right - angle bends in the pipe cleaner at the muzzle end. This crank is rotated to wipe the internal surface of the barrel (Fig. 8).

6. The crank is straightened out and cut flush with the muzzle (Fig. 9).

7. The pipe cleaner is withdrawn from the breech end (Fig. 10) and freshly prepared benzidine solution is added to detect traces of blood.

In a similar way, rifles and shotguns were also tested.

Results of this research were not difficult to interpret. The correlation of data, however, was another matter. Initially, an attempt was made to plot dual curves - - one for traces, and the second for more concentrated deposits of blood. The problem of resolving where a trace ended and a heavier concentration of blood began was strictly a matter of personal interpretation.

To simplify this task all results are reported as the maximum penetration of obvious traces of blood. Without exception, heavier concentrations of blood were detected nearer the muzzle of each weapon.

In general several results, summarized in Table 1, were obtained that are quite consistent with what was originally anticipated:

1. The larger the caliber or gauge, the greater the depth of blood penetration into the barrel.

2. Recoil - operated autoloading weapons will produce less depth of blood penetration than a weapon whose barrel does not recoil.

S. The use of magnum or similar, higher energy loads will produce more depth of blood penetration than standard ammunition (.357 versus .38 spl, magnum versus field, etc).

4. When a double - barrel shotgun is discharged at contact, considerable backspatter occurs (up to 12 cm) into the dormant barrel.

Table 1. The Maximal Penetration of Blood into the Muzzles of Various Firearms

Weapon Maximum distance* (inches)

Standards shotguns, 12, 16, 20 gauge 5

Recoil operated, auto-loading shotguns, 12, 16, 20 gauge 2

.308 Winchester 3

.45 ACP (recoil operated) 2

.357 magnum revolver 3

.38 Special revolver 2

.22 revolver 1-1.5

*Maximum discharge distance at which traces of blood were detected to a depth of 5 mm or greater inside the weapon’s muzzle.

In this way, the researchers determined that a relationship existed between discharge distance and the depth to which blood is drawn back into the muzzle of a firearm. However they went ahead to prove that such a relationship works well in actual casework. Its value has been established in several cases.

Captions to figures:

Fig. 1. Hollowing out a head with a propane torch.

Fig. 2. Completed head ready for firing. Note the dark, blood soaked impact area in the top center.

Fig. 3. Test conditions for firing. The shotgun is resting on a support to maintain an accurate discharge distance.

Fig. 4. Effect of impact a fraction of a second after discharge. Blood is spewing out of the flying head.

Fig. 5. Straw, pipe cleaner material, and revolver prior to assembly for swabbing the barrel.

Fig. 6. Swabbing assembly inserted into the muzzle.

Fig. 7. Withdrawal of the protective straw exposing the barrel to contact with the damp pipe cleaner.

Fig. 8. Turning the pipe cleaner inside the barrel to dissolve blood at points of contact.

Fig. 9. Cutting excess pipe cleaner at the muzzle.

Fig. 10. Withdrawal of the pipe cleaner from the breech.

This article has (2501) words

Dr. Anil Aggrawal, M.D.

Professor of Forensic Medicine

Maulana Azad Medical College

New Delhi‑110002