Later On

A blog written for those whose interests more or less match mine.

Archive for February 25th, 2020

A Key FBI Photo Analysis Method Has Serious Flaws

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FBI forensics increasingly seems unreliable. Ryan Gabrielson reports in ProPublica:

A study published this week casts doubt on the reliability of a technique the FBI Laboratory has used for decades to identify criminals by purporting to match their bluejeans with those photographed in surveillance images, potentially undermining evidence used to win numerous convictions.

The FBI’s method, used principally in bank robbery cases, matches denim pants by the light and dark patches along their seams, called wear marks. An FBI examiner’s scientific journal article on bluejeans identification in 1999 argued that wear marks create, effectively, a barcode that is unique on every pair. That article provided a legal foundation for the FBI to use an array of similar techniques to assert matches for clothes, vehicles, human faces and skin features.

After a ProPublica investigation raised questions about the technique, Hany Farid, a University of California, Berkeley, computer science professor and leading forensic image analyst, and Sophie Nightingale, a postdoctoral researcher in image science, tested the bureau’s method and found several serious flaws. Their study, published this week in the journal Proceedings of the National Academy of Sciences, is the first known independent research on the technique’s reliability, even though the courts have allowed bluejeans identifications as trial evidence for years.

The new study determined that seams on different pairs of bluejeans are often highly similar. Separately, multiple pictures of the same pant seam, taken under varying conditions, can appear starkly different from one another.

Taken together, the authors write, these deficiencies show “identification based on denim jeans should be used with extreme caution, if at all.”

The FBI declined to comment on the study.

In its articles last year, ProPublica revealed that FBI examiners have tied defendants to crimes in thousands of cases over the past half-century by using crime-scene pictures in unproven ways and, at times, have given jurors baseless statistics to say the risk of errors in their analyses was extremely low. In several cases, the FBI’s most prominent image examiner contradicted the original conclusions and results in his lab reports when presenting evidence to criminal courts, FBI records and legal filings show.

The FBI’s issues with image analysis echo earlier controversies over other forensic techniques. The bureau’s lab technicians and scientists had long testified in court that they could determine what fingertip left a print and which scalp grew a hair “to the exclusion of all others.” Research and exonerations by DNA analysis have repeatedly disproved those claims, and the U.S. Department of Justice no longer permits its forensic scientists to make such unequivocal statements.

ProPublica found that examiners on the Forensic Audio, Video and Image Analysis Unit, based at the FBI Lab in Quantico, Virginia, continue to use similarly flawed methods and to testify to the precision of these methods, according to a review of court records and examiners’ written reports and published articles. At ProPublica’s request, several statisticians and forensic science experts reviewed the unit’s methods. The experts identified numerous instances of examiners overstating their techniques’ precision and said some of their assertions defied logic.

In response to ProPublica’s reporting, Nightingale and Farid said they decided to test the FBI’s photo comparison techniques, starting with bluejeans identification.

The researchers purchased 100 pairs of jeans from local second-hand stores and collected images of more than 100 additional pairs of jeans through Mechanical Turk, the Amazon service that provides workers to complete tasks. The researchers used four high-resolution pictures of the seams on each pant leg.

They documented wear marks in the same manner FBI examiners do. But the researchers used what is known as signal analysis to digitally convert the patterns into numeric values and calculate how similar the jeans in different images were to each other.

The authors were consistently able to mark the same features, suggesting the first step in the bureau’s process works as intended.

mages of bluejeans seams showing wear collected by the researchers. (Courtesy of Sophie J. Nightingale and Hany Farid)

But then the analysis measured wear mark patterns and found the FBI Lab’s method struggled to match images of the same pant seam, which were frequently no more similar to one another than to seams from different pairs.

Nightingale and Farid hypothesize that denim jeans are too flexible, as the material easily stretches and shrinks, changing how wear marks appear, even moment to moment.

The technique failed to correctly match images of the same bluejeans in most cases unless they allowed for a high rate of false positives. When inaccurate matches were limited to one in 10,000, it identified less than 30% of the true matches.

Ultimately, comparing bluejeans seams is relatively useless, Farid said. “If you’re willing to tolerate that only one in four times this will be useful, OK, fine, use the analysis.”

Brandon Garrett, a Duke University law professor who studies the reliability of forensic science, . . .

Continue reading.

Written by Leisureguy

25 February 2020 at 5:03 pm

Taking the bus

with 2 comments

I fear this will be a post that causes much eye-rolling among many readers, but I have never had much bus experience at all. I grew up in a small (pop. 2400) town that had no bus service. In college, in another small town, I never took a bus but simply walked: the college was close enough to downtown that the walk was just a few blocks, and I never felt the need to go elsewhere.

Then upon graduation, I bought the first in a succession of automobiles and simply drove everywhere. I did occasionally take a bus — on business trips to Denver, I would routinely take the bus from the airport to my downtown hotel, because it was very inexpensive and the stop was right by the hotel. But bus rides were rare, and I never even considered exploring (say) Denver by bus.

Now, however, I can see where I might want to minimize driving. So I am learning to use the bus, something a great many people know very well. I am a beginner at heart, and I like to help other beginners (thus, for example, the shaving book, and my various posts on cooking and cooking discoveries and experiments), so now I am a bus beginner and will write for other beginners.

The first observation is that people who ride the bus wear good walking shoes, because there is inevitably a fair amount of walking (from the bus stop to the actual destination, for example). The second observation (particularly with the rapid spread of the coronavirus) is that there a great many surfaces that many people touch: the grab bars.

I think I’ll probably buy cheap disposable poly gloves (the sort food-handlers wear). They cost about 1¢ per glove, and it would be easy to carry a roll of them in a coat pocket: use it on the bus, discard at destination. I didn’t see anyone doing this, but if the pandemic really gets going, I would have no problem using hand protection. People wear breathing masks (ineffective), but gloves would be a much better idea. (I already use my elbow rather than my hand to press elevator buttons and the press-plate that opens “automatic” doors. In flu season, frequent washing of hands is a good practice, but an ounce of prevention is worth a pound of washing.)

The upcoming stop is clearly displayed in the bus with LED signage, and when you’re at a bus stop you can text the bus stop ID number (on the sign) to the bus authority and get an immediate reply giving the times the next four buses will arrive at the stop, identifying each with the route number. In addition, for any route the app NextRide will show you a map with stops market and with (moving) icons for the buses on the route (their real-time location). Technology has helped.

Nowadays buses, like ambulances, are much more purposed-designed, with a kind of engineering aesthetic that emphasizes functionality. For example, buses now are built for accessibility — they no longer have steps leading into the bus (the entrance platform is close to sidewalk level), and they readily accommodate walking aids (medical walkers).

Senior citizens (and students) generally seem to get a break. I don’t get a free pass, but the monthly pass for me is about half what a non-senior adult would pay. And with a monthly pass, I can do a lot of exploring.

One great benefit I already see: no worries about parking — the whole issue vanishes. As a long-time driver (and parker) of cars, that seems wonderful.

You with years — even decades — of experience in riding buses are doubtless astounded by my naïveté, but I am writing this not for you but for those who, like myself, have been car-bound (including driving around looking for a parking spot) for years. Relying on the bus is an interesting change and adds a transportation option that has some significant advantages.

And, BTW, I have yet to ride Uber or Lyft. (I do, however, have a fair amount of experience in taking taxis.)

UPDATE: I got this note from The Eldest, who works in the Johns Hopkins School of Public Health:

Wearing gloves not recommended. Hand-washing is better. For those who aren’t accustomed to wearing them, they end up transmitting more virus through a false sense of security and lack of understanding of the protocols for use. Plus plastics pollution. Best practice is 20 second (timed) hand washing with warm water and soap.

Written by Leisureguy

25 February 2020 at 1:53 pm

Posted in Daily life, Health

Shaving cream and starting a three-razor comparison

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I exchanged emails yesterday with someone who brought up shaving cream, and I decided to indulge a while in shaving creams, beginning with this one that The Wife brought back from Paris.

Using my RazoRock Keyhole brush, I easily got a good lather, and set to work with my RazoRock MJ-90A. A reader wanted to know how the MJ-90A, the Edwin Jagger, and the Rockwell 6S razors compared, so I’ll be using those, starting today with the MJ-90A — which did a fine job, much better in fact than the Woodturners Catalog slant. Three passes left my face totally smooth, with no touch-up required.

A good splash of Alt-Innsbruck, a wonderful aftershave, and the day is launched.

Written by Leisureguy

25 February 2020 at 7:57 am

Posted in Shaving

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