Posted on December 00, 0000 in Criminal Defense
Inside a courtroom, and to a jury, a DNA sample almost always seals the case against an alleged criminal; it would seem appropriate, considering how the odds of a false identification is lower than one in 10 million. But real and valid cases of DNA contamination - from the “trace” DNA samples that can be transferred by a mere handshake, to a single intact sperm inadvertently finding its way onto a slide containing a woman’s vagin*l secretions – suggest that our reliance on DNA evidence has become more than slightly concerning.
DNA Evidence – Then and Now
When DNA analysis first emerged, a decent amount of evidence was needed to extract just a partial profile (think a blood stain the size of a quarter). But, as modern science has improved, the sample of DNA needed to supply incriminating evidence has decreased exponentially. Today, an entire profile can be created with a sample the size of a pinhead. Unfortunately, that improvement has come at a price; and quite often that price is the wrongful conviction of an innocent person.
Transfer of DNA by Insects
Forensic biologist Annalisa Durdle has spent years studying flies and their ability to transfer DNA evidence onto a crime scene. During that time, she has made some shocking discoveries – many of which challenge information considered common forensic knowledge. For example, human sem*n, particularly dried sem*n, happens to be a favorite of flies. If enough is made available, they will eat it until it kills them. Blood, although considered a viable source of food, is less desirable, but it can still easily be transferred to a crime scene through fly fecal matter or vomit.
Analysts often use what they know about flies to rule out whether or not a sample could have been left behind by a person or if the evidence was simply left behind by a passing fly. Unfortunately, even the habits of flies are highly misunderstood. Thought to prefer sun-warmed areas of ceilings, walls, windowsills, and light fixtures, the scientist found fly excrement in poorly lit areas, in lower areas of the room, and often in places that were far from a food source. Of equal concern is that, when analyzing DNA, forensic scientists have no method for determining whether a specimen is sem*n or fly excrement.
Of course, this is not completely new information; forensic scientists have used the excretions of flies, mosquitoes, and even larvae to place people at the scene of a crime or in the life of a victim. However, this new evidence shows that, even if the victim had no prior history with an alleged criminal, DNA profiling might suggest otherwise. As a result, people could (and probably are) wrongfully convicted of a crime they never committed.
Knowledge Is Power in Your Criminal Case
Effective handling of a criminal case requires more than just knowledge of the law; it requires innovation, creativity, exceptional investigatory skills, constant education, and a willingness to search below the surface. The experienced and skilled Milwaukee criminal defense attorneys at Gimbel, Reilly, Guerin & Brown, LLP possess these traits and are willing to go the extra mile in helping you build a solid criminal defense. Get the representation you deserve. Call 414-271-1440 and schedule your consultation today.
Source:
https://cosmosmagazine.com/the-future/framed-fly
FAQs
Crime Lab scientists analyze evidence and develop a DNA profile of a possible suspect. That DNA profile is used to search the DNA database, known as the Combined DNA Index System (CODIS). If the DNA sample searched against CODIS matches a DNA sample already in the database, that is known as a “hit.”
What forensic evidence can be used in DNA testing? ›
Flakes of skin, drops of blood, hair, and saliva all contain DNA that can be used to identify us. In fact, the study of forensics, commonly used by police departments and prosecutors around the world, frequently relies upon these small bits of shed DNA to link criminals to the crimes they commit.
What can a DNA profile tell a forensic scientist? ›
Forensic scientists can use DNA profiles to identify criminals or determine parentage. A DNA profile is like a genetic fingerprint. Every person has a unique DNA profile, making it very useful for identifying people involved in a crime.
Are flies attracted to dried blood? ›
“It was also interesting to find the flies generally preferred dry blood or sem*n to wet blood or sem*n,” Durdle says. “This could be important, because it means flies could continue to cause problems at a scene long after the biological material had dried.”
What method do forensic scientists analyze DNA by? ›
The most common form of DNA analysis is called polymerase chain reaction (PCR). The development of PCR testing has greatly advanced the field of forensic DNA testing by increasing the success rate of the analysis of old, degraded, or very small biological evidentiary samples.
How accurate is DNA evidence in forensics? ›
If investigators properly collect and handle biological evidence and forensic scientists employ accepted methods and conduct the analysis correctly, DNA evidence is extremely accurate. The chances of one person's DNA profile matching another person's is minimal—about one in a billion by some estimates.
How do you identify a DNA profile? ›
Once forensic scientists obtain a sample, they extract the DNA from cells in bodily fluids or tissues and copy it. They then separate the copied markers using a process known as capillary electrophoresis. This enables them to identify distinct markers and the number of repeats for different markers in each allele.
What are the sources of DNA evidence? ›
DNA is contained in blood, sem*n, skin cells, tissue, organs, muscle, brain cells, bone, teeth, hair, saliva, mucus, perspiration, fingernails, urine, feces, etc. Where can DNA evidence be found at a crime scene? DNA evidence can be collected from virtually anywhere.
Can DNA be transferred by touch? ›
Touch DNA, also known as Trace DNA, is a forensic method for analyzing DNA left at the scene of a crime. It is called "touch DNA" because it only requires very small samples, for example from the skin cells left on an object after it has been touched or casually handled, or from footprints.
Can flies drink your blood? ›
Biting flies feed on blood, attacking humans and other animals as food sources. Some are capable of transferring disease through these feeding habits.
Indeed, insects are capable of nociception, so they can detect and respond to injury in some circ*mstances [3]. While observations of insects' unresponsiveness to injury warrant further research, they ultimately cannot rule out insect pain, particularly in other contexts or in response to different noxious stimuli.
What color is a fly's blood? ›
The blood of flies is similar to the blood of most insects, which is clear or clear with a slight tint of yellow and green. In part, this is because insects have open circulatory systems that mix their blood with the interstitial fluid surrounding their tissues.
How can DNA be used to identify criminals? ›
As such, it can be used as evidence to help convict a suspect of a crime, but also to clear an innocent person. Samples from crime scenes or suspects, usually obtained from blood, hair or body fluids, are analysed, resulting in a DNA profile which can be compared against other profiles within a database.
How can DNA be used as evidence? ›
DNA is a powerful investigative tool because, with the exception of identical twins, no two people have the same DNA. Therefore, DNA evidence collected from a crime scene can be linked to a suspect or can eliminate a suspect from suspicion.
How is DNA used to identify individuals? ›
The DNA marker is used to identify the specific genetic variations an individual possesses. DNA Profile: A set of genetic characteristics that results from forensic DNA analysis of several DNA markers. DNA Typing or Profiling: The process of testing to identify DNA patterns or types.
How can DNA be used to fingerprint a suspect in a crime? ›
The naturally occurring variations in the DNA form an identity profile unique to each individual. The DNA identity profile from the biological evidence gathered at the scene of a crime is compared to the DNA patterns of the victim and the suspect.
Inside a courtroom, and to a jury, a DNA sample almost always seals the case against an alleged criminal; it would seem appropriate, considering how the odds of a false identification is lower than one in 10 million. But real and valid cases of DNA contamination - from the “trace” DNA samples that can be transferred by a mere handshake, to a single intact sperm inadvertently finding its way onto a slide containing a woman’s vagin*l secretions – suggest that our reliance on DNA evidence has become more than slightly concerning.