Pride and [ERROR: FUNCTION TERMINATED]

It is a truth universally acknowledged that any homework of significant difficulty is in want of long hours to completion. In this case, twenty hours, give or take some breaks to re-hydrate from where the tears slipped away unnoticed among the frustration and eye strain. Even then, the outcome isn’t what you wanted and you may not make the deadline at all.

May whatever powers-that-be bless professors that give their students who fail part one of a multi-part homework a working version to complete the next section.

All dramatics and literary reference aside, animation is hard. I know this for a fact, I’ve been doing frame-by-frame animation since middle school and, while that can get tedious, it is much, much more straightforward than the computer graphics assignment I was referencing above. However, I’m getting ahead of myself; this is a story about learning, frustration, trial, error, failure, success, and at the end of it all, the final product.

The first thing to note is that Computer Graphics is a known grade killing class, and has been that way for at least five years, if not since it’s conceit. You talk to any Georgia Tech student who has taken the course and they’ll tremble in horror, either fake or very real, the reaction is the same at its core. I, unfortunately, didn’t know this until after I had begun.

The second thing to note is that the professor that I had for the class was infinitely preferable to previous holders of the position, as referenced by the second paragraph.

The third thing to note is that I’m still not entirely sure what a scene graph is. Of course, I understand what it is in concept — a data structure designed to keep graphic elements organised in a certain configuration for ease of use. Say you had a character with the parts: body, head, left arm, right arm, left leg, right leg, left hand, right hand, left foot, and right foot. The graph would be organized something like this:

Body
/           |            |            |             \
Head    left arm   right arm      left leg     right leg
|               |              |            |
Left hand    right hand    left foot    right foot

The character would then be connected to the world of the scene through the Body node. Using this construction, all of the pieces of the scene graph of the character are moved relative to its parent nodes– the nodes above it and connected to it within the scene graph. It’s fairly simple for anyone with a basic knowledge of coding languages, but understanding a scene graph and implementing one are two entirely separate things. It’s the implementation where I stumbled and was left in the dust on the side of the road.

However, homework waits for no one, especially not a homework with multiple parts. Part two of the homework was to create a character using the scene graph implementation from part one, and to connect the pieces appropriately to make a recognizable image of at least ten parts and three levels like the scene graph above. This was accomplished mostly by trial, error, and begging my fellow students to take pity and help me. If there is one thing I can say about college, it really does destroy any pride you may have once had when it comes to school work.

The third and final part of the homework was to take the character from part two and create an animation in the scene graph. Camera movements, movement of at least one part of the character, and one part of the surrounding scene were required. This part came the easiest to me, but it was still an exercise in frustrated guess-and-check. Moving the camera a few degrees only to find you turned it the wrong direction, making sure that the piece of your character that you decided to move doesn’t visually disconnect itself and become a floating arm spinning into the distance.

I’ll admit, I laughed aloud at some of the things my errors caused, but it felt more hysterical than anything at the time. When your entire animation starts spinning into the endless void, you have to start laughing, or you’ll cry. Still, I lived in the TA office hours until I finally managed to create a working product. It isn’t what I wanted, not nearly as good as it could have been, but remember what I said earlier about pride. If it completes all of the requirements and doesn’t look like hot garbage, it is a success.

You can view the finished version that took 20 hours out of my life by clicking the link below.

https://dj-baker.github.io/charged-animation/

Your journey starts here! Let’s talk!

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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.