Francis Emelogu//The Daily Cougar
Just about the entire human population has seen an episode of “CSI.” DNA evidence, a staple in any high-profile court case, can close an old cold case or open up a can of worms. Since its inception in 1985, DNA testing has become the most reliable and dependable physical evidence of any crime scene. Almost three decades later, it seems to have become too heavily relied on, taking out the “good” in good police work.
In the 2010 case for the murder of Vanessa Pham, a college student in Virginia, DNA evidence provided much-needed closure to her family. A forensic test added to the case file linked Julio Blanco-Garcia to the murder of Pham. The Phams waited more than two years before police made an arrest. DNA analyzed from the knife handle showed a mixture from three people, including the victim and Blanco-Garcia.
Blanco-Garcia was sentenced to 49 years in prison.
The case against relying solely on DNA evidence arose in the trial of David Butler. Police failed to produce a suspect in the 2005 murder of Anne Marie Foy. The first investigation returned no DNA matches. In a second run, a sample recovered from a cigarette butt found in 1998 led to Butler matching the DNA profile taken under Foy’s finger nails.
However, the testing procedure was deemed unreliable because the analysis of the DNA under Foy’s nails was done at a time before higher quality for handling samples were established. Even then, there’s a possibility of an innocent explanation for how the DNA got there.
After 11 months of jury deliberation, Butler was cleared.
In the case of the murder of Stephen Lawrence, the convictions of Gary Dobson and David Norris were possible from the retrieval of a minuscule amount of the victim’s DNA on the killers’ clothing.
DNA’s danger of being discredited
The growing use of DNA in court cases poses three problems: human error, contamination and accidents. DNA evidence has now become a shortcut to convictions. The system is not foolproof; if humans are involved, there’s potential for error.
DNA evidence has freed the wrongly convicted and brought the guilty to justice. While it is considered reliable, it cannot always be infallible.
“High-profile cases, such as the Amanda Knox case — acquitted by an Italian court of murdering her flatmate after a trail that hinged almost solely on DNA evidence — have fed the notion that such evidence can now be fought and discredited,” said journalist William Langley in an article for the Telegraph.
Being too dependent on DNA evidence has become a problem. With no obvious motive and a lack of witnesses or confession, there was little in the way of circumstantial evidence. Italian police were unable to present any evidence other than the finding of Knox’s DNA on the knife that was used to kill Meredith Kercher.
American experts suggested that the evidence was mishandled and wrongly analyzed.
This demonstrates how DNA samples could have been contaminated by stray DNA, misinterpreted or have an innocent explanation. DNA should not be the gold standard, because it is not that simple.
How DNA is processed
DNA is the blueprint for everything in the human body. The genetic code makes it nearly impossible for two people to have identical DNA, with the obvious exception of identical twins.
The process of using DNA evidence in court begins with collection. Where fingerprinting used to be the gold standard, collection can be from hair, saliva, blood, semen, skin and sweat. Collection requires only a few cells to be tested.
The sample is then analyzed. Currently, short tandem repeat analysis offers several advantages, the biggest of which being that it requires a much smaller sample of DNA. Through polymerase chain reaction, the small sample can be amplified, because PCR makes copies of DNA similar to how DNA copies itself within a cell.
STR analysis examines how often base pairs repeat themselves in a specific location on a DNA strand. Repetitions of four or five base pairs in samples from PCR amplification are usually what investigators look for, because those are the most accurate.
There are three results when a DNA is tested for a match: inclusions, exclusions and inconclusive results. Inclusions are if the suspect’s DNA profile matches a crime scene DNA profile and the suspect is included as a possible source. Exclusions are if the suspect’s DNA does not match, eliminating the suspect as a source. Inconclusive results can be yielded because a sample was contaminated or there is a small or degraded sample that does not have enough DNA to produce a full profile.
The limitations
Just because DNA from a crime scene matches DNA taken from a suspect does not always mean there’s an absolute guarantee of a suspect’s guilt. Forensic experts talk about the fact that the chance is 1 in 7,000 that an unrelated person would, by chance, have the same DNA profile obtained from evidence.
Often, people get misconceptions of DNA analysis because of how it is portrayed in movies and television. Lawyers and judges complain that the “CSI effect” influences criminal justice. This typically happens when jurors unnecessarily demand a DNA test in cases that rely too much on DNA evidence to the exclusion of physical evidence.
As accurate and popular as DNA evidence is, it should not be the only thing that makes or breaks a court case. It is only part of the bigger picture, and “old-fashioned police work” should always be taken into consideration. Without a motive or physical evidence taken from a crime scene, DNA evidence is just DNA. Like anything else, it’s not always absolute.
Opinion columnist Gemrick Curtom is a public relations junior and may be reached at [email protected]
A british DNA scientist (David Balding at University College London) said: Knox was )not at the crime scne. The probability than Amanda Knox where on the crime scene is nearly zero. Raffaele Sollecito was probable not there, but he could be there with a small probabilty.
An American Scientist (Dr Hampikian) said to the alleged murder knife: “there was no evidence of blood or any other body fluids found …You can’t really wash the blood off and leave the DNA in any practical sense. That means that the few cells or molecules might have been from the laboratory after they amplified Miss Kercher’s DNA.”
BBC: “From the initial collection of items at the scene of the murder, significant traces of just two people’s DNA were found – that of the victim and one other person, Rudy Guede.”
I think Rudy Guede did it by himself. Italy needs to let more Rudy Guede’s move into their country.
There is serious doubt that the knife mentioned above was used in the murder. It was taken out of a drawer of knives in Raffaele Sollecito’s apartment by a Perugian policeman who said it looked cleaner than the rest of the knives therefore, it must be the murder weapon which Amanda and Raffaele cleaned and then put back in the drawer. The only DNA found on the knife belonged to Amanda which makes sense as she cooked in Raffa’s apartment. Further no blood was found on the knife…only starch which probably came from cutting bread. Also, the knife was too large to have made the fatal wounds in Meredith’s neck and does not fit the bloody profile of a knife found on Meredith’s bed.
Rudy Guede was known to carry a smaller knife. He threatened a person with his knife during one of his several local burglaries (for none of which was he either arrested or jailed?!). He possibly abandoned the knife in the canyon outside Meredith’s house when he fled the crime scene. There has been no evidence that a search was ever made for it by the Perugian police.
Finally, copious amounts of Guede’s forensic material was found all over Meredith’s tiny bedroom and in and on her body (as well as her clothes, and inside her purse). Guede’s bloody handprint was found on the wall. No forensic material belonging to either Amanda Knox or Raffaele Sollecito was found in the room.
The knife was just a random knife. Not the murder weapon, not even similar to it.
That’s another weird effect, isn’t it? Produce a knife in court, call it Exhibit A or whatever, and everyone automatically assumes it must be the murder weapon. Even this columnist who otherwise makes excellent points. People are so ready to believe what they are told.
“Italian police were unable to present any evidence other than the finding of Knox’s DNA on the knife that was used to kill Meredith Kercher.”
Actually NO, the knife police chose at random from a kitchen draw in Sollecito’s apartment because ‘it looked shiny’, was incompatible with 80% of the knife wounds, was incompatible with a bloody outline left on the bed sheet, with the knife actually used to kill Ms Kercher, and was never shown to be the murder weapon.
The DNA expert in the U-tube presentation, “The Case for Innocence”, recorded at UW during the first appeal, stated that the same result could have been obtained with any knife from anyone’s kitchen draw, if the same tests had been done at the same lab, with the same technicians.
The failure of the DNA evidence in the knox case in no way is a reflection on the underlying science, but only a reflection on the misuse, and outright fraud by the prosecution in the case against Knox & Sollecito, through the misrepresentation of their results, methodology, and willful concealment of such from the defense.
Good catch – “alleged murder weapon” would have been a better choice. It’s amazing how an otherwise well written article can be ruined by mistakes like this.
DNA evidence does not leave a time stamp, unlike Guede’s bloody palm print made after Meredith was wounded and before the blood coagulated. Furthermore, Amanda’s DNA should have been found where she lived. Amanda’s DNA doesn’t prove anything, never has and rarely could.
DNA – Do Not Accept!