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Dive Log

January 25, 2012 0Comments

In this day and age, it is so very common to lose ourself in the monotony of our daily lives, the sound as our heels hit the pavement, rustle of the leaves as we pass by the bus stop on a particularly windy day. We get so accustomed to the way our skin sloughs off the water from our shower in the morning that we don’t take the time to notice that that compound, that deliciously ever-present H2O, covers more than half of the earth, and without it, our bodies would cease to function.

We also forget the intense beauty that exists in our oceans.

Most people never get to experience what it is like to simply immerse themselves in an aquatic environment. Yes, aquariums, like the one in my home state of Georgia, are fantastic for getting to observe the wonderful creatures that we would otherwise never have a chance to interact with. But it’s not enough for some people.

It’s not enough for me.

Over my winter break, on the second to last day of 2011, I went on my first ever real dive. While I am not SCUBA certified, my mother and I were able to find an alternative called SNUBA diving. The concept of a SNUBA dive is the same as SCUBA dives; you go down with a breathing apparatus, deeper than you could while free-diving, but your air supply is a raft at the water’s surface instead of a tank on your back. It was a wonderful experience for someone unable to go on dives otherwise.

It got me thinking, though. The reefs off of the Florida Keys were once as beautiful and vibrantly alive as those off the coast of Texas or even those in Australia. Now, though, they are sick. While fish were obviously there, they lived in very small patches of the reef. Corals of all kinds were dying, grey and fragile. The occasional nurse shark brushed by as my brother, our instructor, and I visited its home, but the ecosystem was clearly suffering. Our instructor told me later that the reefs were getting more and more sparse for observational divers like myself.

Those reefs, and many others, are on the verge of dying. That dive made me face the death of every single small polyp in those reefs. But their dying brought to life in me a spark of inspiration. It brought to life my motivation for getting my degree in biology, for getting certified in SCUBA diving and figuring out how to spread the word of our dying reefs.

Secretly, about to become not-so-secretly, that is my belief in this, Charged Magazine. It is my hope that you, dear reader, are not stuck listening to the ins and outs of chemical reactions, or trying to figure out how the Krebs cycle works, or why the fifth derivative of a function is actually important in the real world. It is my hope that you find something in the real world, something tangible, that makes you passionate. For me, that passion is the ocean, and how I want it to become a place of endless wonder, not endless fear, for the human race.

On behalf of the entire Charged staff, present and future, I welcome you to a world of inspiration, a world of explaining miracles. I welcome you to the world of science.

Above are some shots from my dive.

For more pictures from other dives, I recommend visiting www.abelic.net/

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Margeaux Comerford
About Author

Margeaux is a psychology major at Georgia Tech, who works in cognitive psych research. In addition to working for Charged, Margeaux spends her free time attempting to teach herself guitar, pursuing a passion in photography, and speculating on the time paradoxes created in the show Doctor Who.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.