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Fallible Fingerprints

Posted on March 20, 2019 | 3 comments

Before DNA evidence became the golden standard for forensic labs, convicting a criminal often meant dusting the crime scene for prints.

All forensic evidence are liable to error and fingerprints are no exception. In general, there are two types of error: false negative and false positive. A false negative occurs when the two fingerprints are a match but the examiner declares the fingerprints to be different. A false positive is when two fingerprints are not a match but the examiner concluded otherwise. In both cases the consequences are different, while false negatives may not entirely exonerate a criminal, false positives can lead to wrongful convictions where an innocent person can face jail time for something they did not do.

Example of a fingerprint Source: Wikimedia Commons

There are eight common fingerprint patterns: arches, tented arches, right loops, left loops, plain whorls, central pocket loops and double loops. When the lines or ridges on a finger develops and meets other ridges, the two ridges can interact in many ways, resulting in what is called a minutiae. Since fingerprints depend both on genetic and environmental factors, the patterns developed are very unique. Even identical twins can develop different fingerprints. However, theory and practice can be very different. In the modern age, there still is not a definitive certainty in how unique the match between fingerprints are. It was claimed that a false positive was one in 64 million. In one study, researchers found fingerprint exams had a false positive error rate of 0.1% and a false negative rate of 7.5%. These numbers show that human error and the quality of fingerprints can significantly influence how forensic experts perceive the evidence.

In the famous case of the Madrid train bombings, Brandon Mayfield was wrongfully convicted based on fingerprints that were found at the scene due to poor quality of the fingerprints. Later on, when the five fingerprint experts were asked to re-examine these prints, three experts reversed their conclusion and claimed the results were inconclusive. In conclusion, while fingerprints are a useful tool, they are not infallible and prone to human error more than one expects.

(1)
Knapton, S. Why Your Fingerprints May Not Be Unique. The Telegraph. March 14, 2016.
(2)
The “CSI Effect.” The Economist. April 22, 2010.
(3)
Statement on Brandon Mayfield Case https://www.fbi.gov/news/pressrel/press-releases/statement-on-brandon-mayfield-case (accessed Mar 20, 2019).
(4)
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach. 249.
(5)
Latent Print Examination and Human Factors Improv.Pdf.
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God’s signature: DNA profiling, the new gold standard in forensic science. – PubMed – NCBI https://www.ncbi.nlm.nih.gov/pubmed/12798816 (accessed Mar 20, 2019).
(7)
Stephanie. False Positive and False Negative: Definition and Examples https://www.statisticshowto.datasciencecentral.com/false-positive-definition-and-examples/ (accessed Mar 20, 2019).
(8)
Photographer, T. English: Fingerprint; 2009.
(9)
Spiro, R. Do Identical Twins Have Identical Fingerprints? | Washington State Twin Registry | Washington State University. Washington State Twin Registry, 2015.
(10)
14 Amazing Forensic Science Techniques.
(11)
8 Most Common Fingerprint Patterns. Touch N Go, 2017.

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Fast, Faster, Fastest

Posted on March 2, 2019 | Leave a comment

Fast, Faster, Fastest

List of the world’s fastest 100 meter sprinters. Shorter time is better. Data retrieved from rankings.com

From horses to cars, trains to spaceships, many aspects of the world are happening in smaller time frames. For example, from Carl Lewis’ 1984 Olympic performance to Usain Bolt’s 9.58 s record at the Beijing Olympics. However, while sprinting has been slowly reaching its plateau, computational power has been exponentially growing.

Exponential growth of computational power over time

Modern day computers run at incredible speeds thanks to the even faster networks that have been developed today. From vacuum tube transistor to the 10 nm technology rolled out from Intel. Moore’s law is based on an observation by Gordon Moore, which found that the number of transistors that can fit inside an integrated circuit doubles every two years. 

Since 2017, Moore’s law has shown signs of stagnancy. It should have been obvious that at some point, this prediction would no longer hold up simply due to the physical limitations of shrinking the transistor size. With contemporary technology, the resources of constructing a CPU (Central Processing Unit) with 14 nm transistors, which is equivalent to 70 Silicon atoms, is entirely feasible. When transistors begin to approach the size of electrons, not only is it harder to trap electrons which are what makeup electrical currents inside the computers and dictate the 0’s and 1’s bit of information stored on the computer, manufacturing these smaller transistors also poses a problem as well. CPUs which essentially the brain of the computers, are made up of dies cut from large silicon wafers which need to made from pure silicon (99.9999%). The problem is to make the patterns on the die, one needs to have a laser source that is already much smaller than the wavelength of purple light: 400 nm. Lasers with shorter and shorter wavelengths are being used and eventually similar to microscopes the wavelengths of light are not longer able to be manipulated smaller and other sources will have to be used.

While the future seems uncertain on the fate of future computers, it is also amazing to think that computers that were used to launch mankind onto the moon are now dwarfed by the power of electronic devices that fits into our pockets. For the vast majority of consumers, it is not how fast the computer runs that dictate our productivity but how we decide to utilise it.

References:

(1)
http://www.umsl.edu/~siegelj/information_theory/projects/Bajramovic/www.umsl.edu/_abdcf/Cs4890/link1.html?fbclid=IwAR13eqZfAC6YzT0D16eWYz3goDs3BdUtmIbrIIxgc0D7Fy9uOcl8W8tw8ck (accessed Mar 2, 2019).
(2)
From Sand to Hand: How a CPU Is Made. Geek.com, 2009.
(3)
Jurvetson, S. Moore’s Law over 120 Years; 2016.
(4)
Top Ten Fastest 100 Meter Sprinters in History https://www.rankings.com/sports-track-sprinters/ (accessed Mar 2, 2019).

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Not so green cars

Not so green electric cars

Nowadays with the rise of renewable energy and improvements in rechargeable batteries, buying an electric cars over a traditional gasoline car is becoming cheaper and cheaper. With greenhouse gas (GHG) emissions reaching new highs every year, an electric car is also becoming the more responsible choice.

The four major renewable energy sources in Canada from 2006 to 2016 in megawatts (MW). Source: Natural Resources Canada

However, though an electric car’s engine does not produce any carbon dioxide gas compared to conventional gasoline engines, many consumers often forget the hidden GHG emissions cost from when a car is manufactured.

Sale of plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs) in China by year between January 2011 and December 2018 | Source: Mario Roberto Durán Ortiz

In fact, from the moment a car comes out of a manufacturing plant, it would have produced as much as 35 tons of CO2 into the atmosphere. Compared to an average gasoline-powered car that produces 4.6 metric tons of CO2 annually, that is more than seven years of emissions from the plant to the dealer.

In addition, not all electric vehicles are made equal. A plug-in hybrid vehicle (PHEV) still has an internal combustion engine; however, it will use battery power for a certain distance before it switches to gasoline as the fuel source. This combines the strength of both gasoline and battery power since there are no emissions for short trips such as commuting to work but also has the flexibility of being able to quickly refill at a gas station. Battery electric vehicles (BEV) or all-electric vehicle is, as the name suggests, run purely on battery power. These vehicles usually have lower maintenance costs due to lacking the moving parts in the internal combustion engine but initial investment and possible replacement battery in future repairs can be quite costly.

Therefore, even if one were to buy an electric vehicle whose fuel solely comes from renewable energy, it would still leave an initial carbon footprint equivalent to sevens years of GHG emissions.

This discrepancy between what we perceive as beneficial for the environment versus what would practically reduce one’s emissions leaves something to be desired. After all, if buying electric vehicles barely changes one’s total GHG emissions, what would be a better way to save the planet?

Cover of the game “reduce reuse recycle” by Nadine3103

Turns out, it all comes back to the principle of reduce, reuse and recycle. In the modern age, every product that uses plastic and rare metals in some way have to refined or synthesized; this means usually in a plant or mine that most likely emits tonnes of GHG. By using old phones longer, supporting local businesses and buying in season products, emissions associated with long-distance transportation can be significantly reduced. Combined with walking and biking more often, these small actions can have more meaningful impacts than buying a brand new vehicle.

Tesla Model S 90 D by Peteratkins. Modified by Mariordo

So the next time an electric vehicle advertises zero carbon emissions, think twice about what would actually help the planet rather than buying the newest technology that may not be as green as it seems.

References

  1. Deutsch: Tesla Model S 90 D; 2017.
  2. Ortiz, M. R. D. Electric Car Use by Country; 2019.
  3. Electric Vehicle Battery: Materials, Cost, Lifespan https://www.ucsusa.org/clean-vehicles/electric-vehicles/electric-cars-battery-life-materials-cost (accessed Feb 14, 2019).
  4. English: Cover of the Game “Reduce Reuse Recycle.”
  5. US EPA, O. Global Greenhouse Gas Emissions Data https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data (accessed Feb 14, 2019).
  6. US EPA, O. Greenhouse Gas Emissions from a Typical Passenger Vehicle https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-typical-passenger-vehicle (accessed Jan 24, 2019).
  7. Clarke, S. How green are electric cars? http://www.theguardian.com/football/ng-interactive/2017/dec/25/how-green-are-electric-cars (accessed Feb 14, 2019).
  8. Infographic: The Evolution of Battery Technology https://www.visualcapitalist.com/evolution-of-battery-technology/ (accessed Feb 14, 2019).
  9. Berners-Lee, M.; Clark, D. Manufacturing a Car Creates as Much Carbon as Driving It. The Guardian. September 23, 2010

 

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Posted on January 23, 2019 in Issues in Science

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