“The American Sherlock takes the stand,” published here last August, is still quite informative about the pioneer criminologist Edward O. Heinrich. This new note simply shares some first impressions after reading his testimony in the transcripts of People vs. Arbuckle. These show how the science of dactyloscopy—of taking and identifying fingerprints—contributed to the prosecution of Roscoe Arbuckle for causing the death of Virginia Rappe. They also invite a long-overdue reinvestigation.

Heinrich obviously relished the opportunity to explain what fingerprints were, that the pattern of ridges in the form of loops and whorls on fingers and palms were unique to every person from cradle to grave. He explained how fingerprints were lifted from a surface and compared to those taken from a living or dead subject. Heinrich even lectured the jurors on the history of fingerprints. He also described how fingerprints were developed using aluminum powder and the tedious process of using different kinds of microscopes, enlarging photographs, and performing mathematical computations to rule out any doubt. Ultimately, the process came down to probability and points of similarity. Ten or more points were considered a match, based on Scotland Yard’s standard adopted by the identification bureaus of virtually every American police department.

Heinrich also described his work in various police departments, his summer session lectures at the University of California-Berkeley, his memberships in applicable professional organizations, and so on. He provided a list of books by fingerprint “authorities.” But, like many criminologists in the early twentieth century, fingerprint analysis was not his specialization. More often than not, these early practitioners were called upon to analyze handwriting samples. Nevertheless, for Heinrich, a proper criminologist had to make the jump from examining the downstroke of a lowercase f, say, and the hypnotic whorl in a fingertip.

Such evidence wasn’t new to American courts in 1921. Police departments, federal and state governments, even businesses were collecting and keeping fingerprint files. But to the layperson, the science behind them was almost as controversial as natural selection. To criminal defense lawyers and defendants, circumstantial fingerprint evidence was hard to overcome if jurors found it convincing.

Heinrich—and the assistant district attorney who was his handler, Milton U’Ren—had to convince juries that he had been long at work on his own methodology and that fingerprints were hardly a sideline for him. He was presented as a professor, even though he his real title was lecturer at the University of California-Berkeley. He reeled off everything he had done professionally, including taking the fingerprints of enemy aliens during the First World War. He also conducted many experiments, including the application and detection of fake fingerprints. But Heinrich’s work on identifying the faded latent fingerprints of Roscoe Arbuckle and Virginia Rappe on a hotel door was his first real test as an expert witness. The defense quickly apprehended this and that he was mostly self-taught. They pulled out all the stops to discredit not only his findings but his person as well.

During the first trial, Arbuckle’s chief counsel, Gavin McNab, tried to convince the jury that the fingerprints were “spooks,” inferring that criminologists who dealt in fingerprints were as phony as Victorian spiritualists. McNab and his colleagues also never missed a chance to note that Heinrich wasn’t a tenured professor, forcing him to admit that he was only a lecturer at Berkeley.

The defense lawyers scored points with the press for their entertaining cross-examinations, which turned Heinrich into an “egghead”—his pattern baldness made him look the part. But after the first trial ended in a hung jury, in part due to Heinrich’s thoroughness in revealing that room 1219 had not been thoroughly cleaned and wiped down, new tactics were adopted in the second trial.

Arbuckle’s longtime personal lawyer, Milton Cohen, took over grilling Heinrich. He was better prepared. He had pored over the literature and cleverly cherrypicked paragraphs to assert that Heinrich had violated protocols and standards in taking fingerprints, photographing them, and developing them using aluminum powder. The most heinous thing that Heinrich and the prosecution did was not handing over the hotel room door to the police and storing it in the property (i.e., evidence) room. This line of attack, however, only revealed that the district attorneys didn’t trust the police, that some members of the department, even the chief, were cooperating with Arbuckle’s lawyers. (Heinrich also disclosed that he had been followed in the St. Francis Hotel.)

Other avenues of attack included the way that Heinrich glibly introduced his assistant and secretary, Salome Boyle, a senior at Berkeley, to the St. Francis deskman. Heinrich called her “my Watson,” implying that he was some sort of Sherlock Holmes. But Heinrich wasn’t being vain but rather self-deprecatory, indeed, self-conscious of his own appearance and what he looked like in the company of a young woman. Cohen also tried to bait Heinrich with an insinuations that wasn’t reported in the newspapers: the seeming impropriety of a professor locking himself away with a coed in a hotel bedroom well into the night, leaving the jurors to think she couldn’t just be there to hold his flashlight.

The alleged “struggle” between Arbuckle and Rappe, entirely based on circumstantial evidence, was an important theme in the unsuccessful prosecution of the comedian. Most books about the Arbuckle case place little credence in Heinrich’s work. But, given today’s sophisticated scanning technology and computer analysis, perhaps a latter-day criminologist might stress test Heinrich’s results. It would provide a puzzle piece that certainly would force one to take every version of events apart and start over again.