October - November, 2018

Facial Recognition Study

A recent study at the University of York, and published by The Royal Society Publishing, sought to determine quantitatively the number of faces a person knows. The average range was between 1,000 and 10,000, with a final estimate under 5,000.

The researchers, using a participating group of 25 graduate and postgraduate students – ranging in age from 18 to 61 years, and comprised of 15 females and 10 males – tested for the number of faces a person knew; the subject had to both recall (i.e., had to either be able to formulate a clear mental image of the face, or be certain that they would recognize a face if they saw it) and recognize (i.e., had to recognize the face from two different photographic images) the face. Familiar or personally known faces and a database of public or famous figure faces were used in the study; the database was created over a period of three months and contained two images each of 3,441 famous people.

Almost all of the participants recalled an average of 362 personally known faces and 290 famous faces. Overall, levels of recognition were found to be much higher than levels of recall and, while facial recognition without recall was common, facial recall without recognition “was rare or absent.” A recall-to-recognition ratio was determined to be 1:4.62.  Combining the data from the recall estimates for the famous faces with the data for the personally known faces led the researchers to arrive at a final estimate of 4,420 known faces.

Sources:  Ian Sample, “Psychologists’ face off reveals humans can recognise 5,000 people,” the guardian.com, October 9, 2018:
R. Jenkins, A.J. Dowsett, A.M. Burton, “How many faces do people know?” Proceedings of the Royal Society B, October 2018:

Crime Clearance Rates

Unsolved Crimes

Studies have shown that, in the U.S., only about one-half of violent crimes and about one-third of property crimes are reported to authorities. In 2015, for example, the Bureau of Justice Statistics (“BJS”) estimated that 47% of violent crimes (excluding the crime of murder, which is not reported by the BJS) and 35% of property crimes were reported to police; those rates are fairly consistent over time. For example, between 1995 and 2015, the reporting rate for violent crimes ranged from 40% to 51%. The type of crime affects the reporting rate; for example, rapes and sexual assaults were reported at a rate of 33%, simple assaults were reported at a rate of 42%, and robberies and aggravated assaults were reported at a rate of 62%. The type of property involved also affects the rate; for example, general theft crimes were reported only at a rate of 29%. Auto-thefts, however, were reported to authorities 69% of the time.

FBI statistics show that, of the crimes reported to police, only about 46% of the violent crimes and 19% of the property crimes are “cleared” through the arrest and charging of a suspect. Different crimes have different clearance rates. Murders are, on average nationally, cleared at a rate of 62%, which is down from the national average in 1965 when 90% of murders were cleared. Burglaries were cleared on average in 13% of the cases, larcenies and thefts at 22%, robberies were cleared at a rate of 29%, rapes were cleared at a rate of 38%, and aggravated assaults were cleared at a rate of 54%.

Sources:  German Lopez, “The great majority of violent crime in America goes unsolved,” vox.com, March 1, 2017:
John Gramlich, “Most violent and property crimes in the U.S. go unsolved,” pewresearch.org, March 1, 2017:

Police Departments that Issue More Fines Solve Fewer Cases

A recent study published in Urban Affairs Review examined the relationship between the fines and monies generated by police and the clearance of criminal cases. Some cities rely on as much as 10% of their revenue from police-generated fines and fees. The study concluded that, for every 1% of a city’s budget derived from police-generated fines and fees, 6.1% fewer violent crimes and 8.3% fewer property crimes were solved or cleared, particularly in smaller jurisdictions (i.e., with a population of fewer than 28,010 people), where the city may not have the resources to have specialized officers.

Additional adverse effects were found. The more negative contact, e.g., tickets, between the police and the citizens, the less trust there is between the two. Distrustful citizens are less likely to call 9-1-1, which can make it more difficult to solve crimes, and higher unsolved-crime rates lead to further distrust of police. Racial disparities were also found. For example, it was determined that cities with lower tax revenues and lower income residents, often minorities, were more likely to get a greater share of their revenue from fines and fees. It was also noted that every “10% increase in the population of African-Americans in a city was also associated with a 1.1% lower rate of crime clearance.”

The study did not conclude that there was a causality, however, and it was noted that more crime can lead to lowered property values, which means less property tax revenue to a city, which forces the city to rely more on fines and fees.

One reporter concluded that “the effect is the same: relatively law-abiding citizens get taxed for breaking minor laws, while violent criminals and thieves get away with their crimes.”

Sources:  Matthew Davis, “Excessive police fines substantially decrease public safety, study reveals,” bigthink.com, September 26, 2018: 
Rebecca Goldstein, Michael W. Sances, Hye Young You, “Exploitative Revenues, Law Enforcement, and the Quality of Government Service,” sagepub.com, August 11, 2018 [Urban Affairs Review, Abstract and accessing options]:

Touch DNA Developments

Secondary Transfer DNA Could Convict the Innocent

A recent article in Forbes pointed out a danger of “secondary transfer DNA,” or “touch-transfer DNA,” evidence: possible conviction of the innocent. People continually shed skin cells at a rate of tens of thousands each day. Current forensic equipment can detect and analyze DNA from samples as small as 16 cells. The article indicated that there currently are no updated, widespread standards specifically directed to preventing cross-contamination through secondary transfer in testing facilities and that the FBI standards for DNA laboratories were last updated in 2011.

Touch-transfer DNA was first noted in 1997 by an Australian scientist, who found that bits of DNA would transfer with fingerprint markings. Law enforcement scientists have, with better and more sensitive equipment, expanded sampling to many different surfaces and objects, regardless of the presence or absence of other identifying evidence. This resulted in, the article noted, prosecutions based “on DNA from low-template and low-quality samples not connected to other identifying data.” Prosecutors would argue to juries, without distinguishing “the unique nature of touch-transfer DNA and the likelihood of random and innocent touch-transfer origins,” that the presence of DNA was a “smoking gun” of guilt. However, it is possible that a person whose DNA was found at a crime scene may never have had direct contact with the person or object sampled.

The article presents several publicized cases involving transfer-DNA issues. One case, that of Amanda Knox in Italy, found the defendant convicted of murder in 2009 based upon a small amount of the victim’s blood found on a knife in the codefendant’s residence. Even though the knife did not match the wounds sustained by the victim, Ms. Knox was convicted. She was subsequently exonerated in 2015 when the courts were more aware of secondary transfer and touch-transfer DNA cross-contamination.

Another case example was that of a man in California who was arrested in 2012 for a murder because his DNA was found under the victim’s fingernails. The man, who was heavily intoxicated on the night of the crime, could not remember what happened that night or if he had committed a murder. Five months later, during which time the man remained in jail, it was discovered that at the time of the murder the man was in the hospital and the paramedics who had treated and transported him there were the same paramedics who later that night responded to the scene of the murder and had contact with the victim.

The author of the article presented another example to illustrate her point. A person enters a restaurant to meet a business associate, touching the door knob when entering, and the person subsequently shakes the associate’s hand. Were the person’s hand to be swabbed for DNA, it is possible that not only that person’s DNA could be found but also the associate’s DNA and the DNA of a number of other people who had earlier touched the door-handle.

The author concluded her article with two major points: “As of now, anytme we touch a public surface, we remain fair game for criminal suspicion based on touch-transfer DNA.” Also, judges should “sustain defense motions for the exclusion of DNA evidence on the grounds that DNA evidence is confusing and misleading, highly prejudicial, speculative and inherently unreliable.”

Sources:  Marina Medvin, “Framed By Your Own Cells: How DNA Evidence Imprisons The Innocent,” forbes.com, September 20, 2018: 

New Dye to Facilitate Forensic Discovery of DNA

Scientists in Australia have developed a DNA staining dye that can make visible otherwise invisible traces of DNA. The scientists developed a technique of using a DNA binding dye, DiamondTM Nucleic Acid Dye, combined with PCR, to accurately measure “the deposition, collection and amplification of DNA deposited by a range of donors allowing for an accurate determination of the shedder status of individuals.”

One of the scientists, Paul Kirkbride, was quoted in a recent news article as saying, “Fingermarks such as these can be very valuable because it is now well-known that they could contain the DNA of the person who left the mark … At a crime scene, or on objects submitted to the lab, such a smudge of DNA is often invisible. Therefore, the DNA analyst or crime scene examiner is forced to carry out their work blind.”  The new testing can reveal how much DNA was shed by a person, whether a person is a shedder, and could aid in determining the last person to come into contact with an object.

Sources:  James Rogers, “DNA deep dive: Scientists devise new forensic dye to catch criminals,” foxnews.com, October 8, 2018:
Piyamas Kanokwongnuwut, Belinda Martin, K. Paul Kirkbride, Adrian Linacre, “Shedding light on shedders,” sciencedirect.com, Forensic Science International: Genetics (Vol 36, pages 20-25), September 2018:
Flinders University, “More reasons for criminals to get caught,” flinders.edu.au, October 5, 2018:

by Neil Leithauser
Associate Editor