Contents
A. The Literary Beginnings ... 22 B. Evolution of the Practice... 29 1. Physical Evidence... 29 a. Biological Evidence — Who? ... 29 b. Nonbiological Evidence — What, How, Where? ... 35 i. Documents ... 35 ii. Physical Match ... 35 iii. Trace... 35 iv. Firearms ... 36 v. Drugs ... 38 2. From Generalist to Specialist (and Back Again) ... 40 C. Evolution of Concept ... 43 1. Transfer ... 43 2. Individualization ... 45 a. Biological Evidence ... 45 b. Nonbiological Evidence ... 52 c. Uniqueness vs. Common Source ... 54 3. Identification... 54 4. Association ... 56 5. Reconstruction... 57 D. The State of the Practice ... 62 1. Continuing Themes... 62
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Figure 2.1 Dr. Paul Kirk. Dr. Paul Kirk both searches for and collects evidence with one of his inventions. Dr. Kirk pioneered many technical and conceptual advances in criminalistics. He proposed that individualizing the evidence that we find is the defining principle of the criminalistics effort. (Courtesy of Bancroft Library, University of California, Berkeley.)
22 Principles and Practice of Criminalistics
a. Recognition and Collection of Evidence ... 62 b. Is criminalistics an Autonomous Scientific Discipline? ... 64 c. Is Criminalistics a Profession?... 65 E. Summary ... 66 References ... 67
It was a dark and stormy night; the rain fell in torrents — except at occasional intervals, when it was checked by a violent gust of wind which swept up the streets (for it is in London that our scene lies), rattling along the housetops, and fiercely agitating the scanty flame of the lamps that struggled against the darkness.
Edward George Earl Bulwer-Lytton
—Paul Clifford, 1830
As with any endeavor, it is useful to study the lessons of the past so that one can at least make new mistakes rather than recycle the old ones. For reasons that remain unclear to the authors, those involved, either integrally or periph- erally, in the practice of forensic science seem to insist on repeating the same mistakes over and over again. In this chapter we identify the roots of forensic science, trace some of the history, and highlight the evolution of concepts as well as practice. We hope that a brief reflection on the past will prove useful in guiding the future course of forensic science. Please refer to Appendix A for a Timeline of Forensic Science.
A.
The Literary Beginnings
From its inception, forensic science has evoked an air of mystery and intrigue. It is probably both the least understood and most misunderstood of all scientific disciplines. Because speculation immediately expands to fill an informational void, rumor and gossip have become the stuff upon which the lay public judges the forensic profession. Certainly, forensic practitioners have historically contributed to the perception that the reconstruction of a criminal event from limited evidence can only be achieved by a few talented individuals with a special aptitude for such work. Even those whose methods were scientifically defensible could not resist encouraging the bit of celebrity and notoriety that seems to follow those known for solving difficult crimes. The accordance of these attributes, combined with the understandable inabil- ity of legal professionals to separate true experts from charlatans, has unfor- tunately also encouraged a proliferation of self-appointed experts whose motives are based solely in greed and infamy.
However, even the most scientifically inclined and professionally oriented forensic practitioners have historically overestimated their ability to draw grand conclusions from limited data. This may follow, at least in part, from the literary beginnings of criminal investigation. In these stories, fictional detectives were able to recreate an entire detailed sequence of events from a few small clues. An example is found in one of Voltaire’s lesser-known works,
Zadig, written in 1747. The chapter entitled “The Dog and the Horse” takes place in ancient Babylon (Voltaire, 1748).
Zadig was walking through the woods when he encountered the Queen’s eunuch and the King’s huntsman. They inquired anxiously whether he had seen the Queen’s dog and the King’s horse. Shaking his head, Zadig asked if they were referring to a bitch, slightly lame with long ears who had recently had puppies, and a horse with small hoofs, about five feet tall and with a tail three and a half feet long. Although he vehemently denied it, the eunuch and the huntsman were in no doubt that Zadig had stolen both the King’s horse and the Queen’s dog, else how could he have known such details? He was arrested, found guilty, and sentenced to flogging and banishment to Siberia.
However, the sentence had scarcely been passed when the missing ani- mals reappeared. The sentence was reduced to a heavy fine to punish Zadig for declaring that he had not seen what he had seen and he was allowed to plead his case as follows:
“… I noticed the tracks of an animal in the sandy soil, which I readily took to be those of a little dog. Some long but delicate furrows, traced in the sand wherever it was raised between the prints of the paws, showed me that it was a bitch with hanging dugs, which must therefore have had puppies a few days before. Other tracks of a different kind, which always appeared to have brushed the sand at either side of the forefeet, showed me that its ears were very long; and as I noticed that the sand was always more deeply impressed by one paw than by the other three, I concluded that our august Queen’s little bitch was a trifle lame, if I may dare to say so.
“As for the horse which belongs to the King of Kings, you must know that as I was walking along the paths of this wood, I noticed some horseshoe prints all at equal distances.… In a straight stretch of path only seven feet wide, the dust had been lightly brushed from the trees on both sides at a distance of three and a half feet from the centre of the path. ‘This horse.’ Said I, ‘has a tail three and a half feet long, which must have swept off the dust on both sides as it waved.’ The trees formed an arcade five feet high. When I noticed that some of the leaves were newly fallen, I deduced that the horse must have touched them, and that he was therefore five feet high also. As for the bit it must be made of twenty-three carat gold, because the horse had rubbed the bosses against a stone which I knew to be touchstone, and which I therefore tested And finally I judged from the marks which the
24 Principles and Practice of Criminalistics horseshoes had left on a different kind of stone that it was shod with silver of eleven deniers proof.”
The king’s court was so greatly impressed by Zadig’s deductive powers that he was promptly vindicated and his gold returned.
In scientific endeavors, advances are commonly foretold in fiction before becoming reality. Forensic science is no exception and the influence of detec- tive literature on the development of modern forensic science cannot be underestimated. Edmund Locard, to whom the concept of transfer is attrib- uted, gives direct credit to Arthur Conan Doyle, innovator of the fictional detective Sherlock Holmes, as the true instigator of modern forensic science. In “The Analysis of Dust Traces,” a three part series published in 1930 in The American Journal of Police Science, Locard wrote:
I hold that a police expert, or an examining magistrate, would not find it a waste of his time to read Doyle’s novels. For, in The Adventures of Sherlock
Holmes, the detective is repeatedly asked to diagnose the origin of a speck
of mud, which is nothing but moist dust. The presence of a spot on a shoe or pair of trousers immediately made known to Holmes the particular quarter of London from which his visitor had come, or the road he had traveled in the suburbs. A spot of clay and chalk originated in Horsham; a peculiar reddish bit of mud could be found nowhere but at the entrance to the post office in Wigmore Street. Nevertheless, one is not to be persuaded that even with the genius of a Sherlock Holmes there would not be the risk of numerous failures in identification of such spots by merely viewing them at a distance. But even such an inspection may develop something signifi- cant and one might profitably re-read from this point of view the stories entitled: A Study in Scarlet, The Five Orange Pips, and The Sign of Four. Elsewhere Holmes insists upon the interest and fascination to be found in collecting tobacco ashes, on which he says he has “written a little monograph concerning one hundred and forty varieties.” (The Boscombe Valley Mystery) On the latter point one should again read The Sign of the Four and also The
Resident Patient (Locard, 1930).
It is worth pointing out several other references by Conan Doyle, a physician by training, to the importance of physical evidence. In “A Study in Scarlet,” Sherlock Holmes devises a specific test for blood which ostensibly improved on the guaiacum test in use at the time. He also points out several attributes of a useful forensic test for blood.
“I’ve found it! I’ve found it,” he shouted to my companion, running toward us with a test-tube in his hand. “I have found a re-agent which is precipitated by haemoglobin, and by nothing else.” … “Why, man, it is the most practical medico-legal discovery for years. Don’t you see that it gives us an infallible
test for blood stains?” … “Beautiful! Beautiful! The old guaiacum test was very clumsy and uncertain. So is the microscopic examination for blood corpuscles.* The latter is valueless if the stains are a few hours old. Now, this appears to act as well whether the blood is old or new. (Doyle, 1887)
In “The Adventure of the Cardboard Box,” he brings to our attention indi- vidualizing attributes of the human ear (Figure 2.2). We also see an example here of literary license in deducing kinship from ear traits.
“As a medical man, you are aware, Watson, that there is no part of the body which varies so much as the human ear. Each ear is as a rule quite distinctive and differs from all other ones. In last year’s Anthropological Journal you will find two short monographs from my pen upon the subject. I had therefore examined the ears in the box with the eyes of an expert and had carefully noted the anatomical peculiarities. Imagine my surprise, then, when on looking at Miss Cushing I perceived that her ear corresponded exactly with the female ear which I had just inspected.” … “Of course I at once saw the enourmous importance of the observation. It was evident that the victim was a blood relation and probably a very close one.” (Doyle, 1893)
It is not unusual, even today, for a young person to choose a career in forensic science because of an early fascination with the Sherlock Holmes stories. In fact, the smoking pipe and deerstalker’s cap have become imme- diately recognizable symbols of crime detection to an entire generation of aspiring criminalists. Unfortunately, the somewhat pompous and omniscient attitude that draws us to Sherlock Holmes as a literary character becomes a liability when transferred to reality. Humbleness and modesty are generally better companions to a seeker of the truth.
Although less commonly recognized in the forensic community, Edgar Allen Poe is credited in literary circles as creator of the detective genre. In an odd twist, Doyle acknowledges Poe’s C. Auguste Dupin as the inspiration for the Sherlock Holmes character (“Study in Scarlet”), and, in typical Holmesian fashion, immediately derides him as an inferior template.
“It is simple enough as you explain it,” I said, smiling. “You remind me of Edgar Allan Poe’s Dupin. I had no idea that such individuals did exist outside of stories.” … Sherlock Holmes rose and lit his pipe. “No doubt you think that you are complimenting me in comparing me to Dupin,” he observed. “Now, in my opinion, Dupin was a very inferior fellow. That trick of his of breaking in on his friends’ thoughts with an apropos remark after a quarter of an hour’s silence is really very showy and superficial. He had
26 Principles and Practice of Criminalistics
some analytical genius no doubt; but he was by no means such a phenom- enon as Poe appeared to imagine.”
Doyle, through the Holmes character, continues his derision of Holmes’ literary predecessors.
Figure 2.2 Locard’s ears. Human ears develop into a wide variety of forms. Edmund Locard collected photographs of ears from numerous people to demon- strate that each one is unique.
“Have you read Gaboriau’s works?” I asked. “Does Lecoq come up to your idea of a detective?” … Sherlock Holmes sniffed sardonically. “Lecoq was a miserable bungler.” He said in an angry voice; “he had only one thing to recommend him, and that was his energy. That book made me positively ill. I could have done it in twenty-four hours. Lecoq took six months or so. It might be made a textbook for detectives to teach them what to avoid.”
In fact, in Poe’s stories, written before the word detective existed, we find several foretellings of forensic concepts that Doyle embellishes for his own stories. It is unlikely to be incidental that Poe establishes Dupin in France, the birthplace of Alphones Bertillon, Edmund Locard, and others comprising a veritable forensic dynasty. He also gives due derision to Eugène François Vidocq, a reformed Parisian criminal, who in 1810 established the first inves- tigative unit ever.
The results attained by them are not unfrequently surprising, but for the most part, are brought about by simple diligence and activity. When these qualities are unavailing, their schemes fail. Vidocq, for example, was a good guesser, and the persevering man. But, without educated thought, he erred continually by the very intensity of his investigations. He impaired his vision by holding the object too close. He might see, perhaps, one or two points with unusual clearness, but in so doing he, necessarily, lost sight of the matter as a whole. (Poe, 1841)
In Poe’s TheMurders in the Rue Morgue, we find possibly the first refer- ence to asking the right question, “It should not be so much asked ‘what has occurred,’ as ‘what has occurred that has never occurred before.’” We also find the forerunner to the famous Holmesian quote “When you have elimi- nated the impossible, whatever remains, however improbably, must be the truth” in Dupin’s “because here it was, I knew, that all apparent impossibilities must be proved to be not such in reality.” Perhaps the most prescient concept introduced by Poe was the application of statistics to the interpretation of forensic results.
Coincidences, in general, are great stumbling-blocks in the way of that class of thinkers who have been educated to know nothing of the theory of probabilities — that theory to which the most glorious objects of human research are indebted for the most glorious of illustration. (Poe, 1841)
And one can’t help but notice the element of the pipe, complete with drifting smoke, introduced in “The Purloined Letter” (Poe, 1845).
Although not known primarily for detective stories per se, Mark Twain (a.k.a. Samuel Clemens) immediately capitalized on one of the most impor- tant developments in police science, individualization using fingerprints. In
28 Principles and Practice of Criminalistics
The Tragedy of Pudd’nhead Wilson, written in 1894, a lawyer with a hobby of collecting fingerprints exonerated twin brothers by showing that bloody prints on a knife were not theirs. From his descriptions, it is quite clear that Twain had carefully studied the theories and capabilities of fingerprints. At least one source indicates that, in 1892, while the details of the plot were still evolving, Twain acquired a copy of Finger Prints, by Francis Galton, and decided to feature fingerprints in the story (Railton, 1998). His proficient use of them in this story certainly predates their wide use and general accep- tance by several years at least.
The fad without a name was one which dealt with people’s finger marks. He carried in his coat pocket a shallow box with grooves in it, and in the grooves strips of glass five inches long and three inches wide. Along the lower edge of each strip was pasted a slip of white paper. He asked people to pass their hands through their hair (thus collecting upon them a thin coating of the natural oil) and then making a thumb-mark on a glass strip, following it with the mark of the ball of each finger in succession.… Some- times he copied on paper the involved and delicate pattern left by the ball of the finger, and then vastly enlarged it with a pantograph so that he could examine its web of curving lines with ease and convenience.
…Every human being carries with him from his cradle to his grave certain physical marks which do not change their character, and by which he can always be identified — and that without shade of doubt or question. These marks are his signature, his physiological autograph, so to speak, and this autograph can not be counterfeited, nor can he disguise it or hide it away, nor can it become illegible by the wear and mutations of time. This signature is not his face — age can change that beyond recognition; it is not his hair, for that can fall out; it is not his height, for duplicates of that exist; it is not his form, for duplicates of that exist also, whereas this signature is each man’s very own — there is no duplicate of it among the swarming populations of the globe! One twin’s patterns are never the same as his fellow twin’s patterns … there was never a twin born in to this world that did not carry from birth to death a sure identifier in this mysterious and marvelous natal autograph.
Interestingly, unlike the other two authors mentioned, Twain reserves his literary license for the story, sticking strictly to the limitations of the tech- nique in his use of fingerprints. Clemens also used fingerprints to further the plot in Life on the Mississippi, in which a thumbprint is used to identify a murderer (Thorwald, 1964).
As we will see in subsequent sections, even the most revered of our forensic forefathers succumbed to an occasional indulgence in overinterpre- tation. Under the current microscope of ever-increasing scrutiny, the current trend is to step back from leaps of intuition. In some cases, this has led to 8127/frame/ch02 Page 28 Friday, July 21, 2000 11:51 AM
an overreaction in the opposite direction, with technical specialists retreating to a corner of the laboratory to provide an isolated analysis of a lone piece of evidence. We suggest that a balance between these two extremes might be achieved by interpreting the evidence with appropriate limitations and in the context of the case.
B.
Evolution of the Practice
As with many applied sciences, the practice of the craft of forensic science evolved undeterred by any restrictions such as fundamental principles or universal concepts. In deference to the order of evolution, we will describe the progress of the profession as it proceeded throughout the last couple of