The Use Of Dna In Plant Forensics Biology Essay

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Forensic scientists are always looking for new ways to use DNA to help investigators solve crimes and to make sense of evidence. As we have learned over the course of this class, every living thing is made up of DNA, and that includes plants. Plants can be extremely key pieces of evidence at a crime scene, which may have been over looked until recently, since DNA has become more widely accepted as a way to classify evidence and make sense of it. The plants and or pollen that are involved in a crime can often times tell a lot about what happened. Botanical evidence can yield a lot of DNA, which can then be researched further to solve crimes or create databases to help scientists and investigators in the future. The use of DNA in plant forensics can be used in death investigation from botanical evidence, to create plant DNA databases from trace evidence, as well as creating STR databases to identify drugs that have been seized.

Collection and Examination of Plant Evidence

As with every other piece of evidence that a forensic scientist examines, it can only be beneficiary to the outcome of the investigation if the crime scene investigator collects all necessary pieces to be examined. If a forensic scientist specializes in testing botanical evidence for DNA to determine the origin of the plant and possibly if a corpse had been transported long distances, then that scientist would need to be given those pieces of botanical evidence to figure that out. So CSI's need to realize that nothing can be over looked at a crime scene because it is almost impossible to know which piece of evidence might contain the key piece of DNA to solve the crime. An article in the Croatian Medical Journal stresses the importance of proper plant evidence collection and preservation if someone is planning to use that to aid in a death investigation. To a CSI, a large branch that is obviously out of place found near a victim would likely be collected as evidence, but as far as grains of pollen, it would not be as obvious to collect them, and they would only be collected if the investigator is already aware of the potential of there being such evidence; and often times extensive training in botany is needed before an investigator would know which plants are indigenous and not (Coyle et al 2005). Once all evidence is collected from a crime scene it must be carefully transported back to a lab for further examination. As with all other forms of evidence, plant evidence can be contaminated; and if the goal is to DNA type that specific piece of plant evidence, if it is contaminated then the results may be false.

Often times at crime scenes if a plant looks out of place they do a DNA test to try and figure out the species of the plant to see if the plant is indigenous to the area or not. Then if the DNA test proves that the species is out of place, then that can give leads about the crime that occurred. Although when the plan is to do a DNA test of a piece of plant evidence, then there needs to be multiple samples from more than one plant of the same species so that the data is valuable enough for comparison and statistical analysis (Coyle et al 2005). So it is going to be difficult to test plant evidence at a crime scene when it appears to be out of place because there might not be anything to make a comparison. But it would certainly not be impossible, because upon further investigation of the area, there may be more clues that all come back to that plant.

Use of Plant Forensics in Death Investigation

There are many DNA plant databases that are created to help keep all the species of plants organized and to make the DNA profiles easier to access for scientists testing plant evidence. These databases also help to outline which species of plants belong to certain areas of the world, and which ones would be out of place if found there. Coincidentally, the databases also help with death investigations that involve plant evidence.

There is a story about a death of a young woman that happened in Taiwan, and when they found her body they were not sure if it was a homicide or a suicide. After a forensics team investigated the body, they noticed that there were stems and berries in her hair that were clearly not indigenous to the area her body was found (Coyle et al 2005). When the investigators did some searching around the area where her body was found they noticed that the evidence in her hair matched plants that were on one of the window ledges of the building by the scene (Coyle et al 2005). Then after further investigation of all of the evidence and the autopsy, they were able to conclude that she had killed herself by jumping and hit her head on the window ledge where the plants were (Coyle et al 2005). So in this case the botanical evidence ultimately solved the case, and because of the plants forensics knowledge of the investigators, and possible DNA plant databases, it was a lot easier.

Botanical Trace Evidence

Plants are everywhere and by default, so is botanical trace evidence. Because plants and plant evidence are commonly found, it can be exceedingly helpful in criminal investigations. Although, like many other fields of forensics science, botanical forensics is not particularly widely used, and there is not a large group of people who are knowledgeable about it. By using forensic botany to identify plants that are found in crime scenes can have a profound effect on the outcome of a case and to test alibis, test the possession of illegal species, and prove the geographic source of the plant (Ferri et al 2009). Since plants are everywhere and there are so many species of plants, scientists needed to come up with a way to make them easier to identify and use, even for people not specialized in forensic botany. So by "taking advantage of DNA sequencing and other bimolecular techniques, identification of land plants becomes useful in forensics, reducing the expertise necessary in botanical identification and producing successful results in casework application" (Ferri et al 2009).

DNA Barcodes in Plant Forensics

To make it a lot easier to identify plants when dealing with forensic casework and trying to work on criminal investigations, having a database of plant DNA that can be used as comparative research is tremendously helpful. So the scientific community has come up with DNA barcodes, created from short orthologous standard DNA sequences to use for species identification, to aid in studies and help with forensic analysis (Ferri et al 2009). Although, for DNA to be viable to become a DNA barcode, it has to have enough information for it to be identified, so if someone found an unknown species at a crime scene and hope to create a DNA barcode for it, that might not be possible if the sample is not large enough. So even though the DNA barcoding can be extremely helpful in establishing a database, it can also be tedious work that might not even give results. There is not yet a universal region used on the DNA, there are still many loci being used to identify plants and that is the most effective, although there have been several loci that have been suggested for universal DNA barcodes in plants (Ferri et al 2009).

DNA barcoding is not a new science; it has been used with animal species based on the mitochondrial cytochrome c oxidase 1 (cox1) (Newmaster et al 2006). But the same DNA sequence cannot be used for plant barcoding because plants do not have the same amounts of mtDNA available as animals do; therefore, it becomes more challenging (Newmaster et al 2006). Because of the challenges that evaluating plant species brings forth, it is terribly beneficial to try and find an area on the DNA sequence that can be universally tested. Scientists are also proposing "the adoption of a tiered approach wherein highly variable loci are nested under a core barcoding gene" (Newmaster et al 2006). The barcoding and DNA databases that are being implemented in forensic botany will help to speed up routine investigations of plant evidence, detection of new species, and aid in the forensic analysis of other, unknown plant artifacts.

Plant Forensics and Drug Sources

Another useful aspect of the DNA databases that are being created via the chosen loci on plant DNA is that illegal drugs that have been seized by law enforcement can be traced back to the source. Just how forensic scientists examine suspects DNA to see which people are linked to specific crimes and which people are not by generating each persons DNA profile, the same can be done with Cannabis plants to track relations. In Connecticut, there were two, seemingly separate drug growing operations that were busted, but then after further investigation into the DNA fingerprints of the Cannabis plants confiscated it was revealed that the operators had been sharing materials (Westphal 2003). This DNA fingerprinting so far only works with Cannabis plants, though, it will not help investigate the origins of cocaine or heroin. But that is still a significant step in the forensic science community to possibly have a way to track all the Cannabis, the most often abused illegal drug, back to where it originated; which might lead to fighting other crimes such as organized crime groups and the black market (Howard et al 2009).

STR Databases for Cannabis

Just as there are general plant databases for the identification of all known and unknown species, there are now specialized databases just for tracking Cannabis using STR markers. There has been a study done that has validated 10 STR loci to identify Cannabis, using only "air-dried leaf tissue (easily obtainable from drug seizure samples)" and now these markers are going to put into a database "to provide insight into the patterns of allelic and genotypic variation within and among seizures or other sample groups" (Howard et al 2009). In the same study, that created the STR database for Cannabis they were able to identify the source of the plant and how the drug was grown; although there is still other information that they were not able to obtain through this process, and that information was, unfortunately, the information that would have made the database much more useful to the forensic community (Howard et al 2009).

In the forensic science community, the discovery of DNA has been monumental to the advancements that have been made. Scientists are continually finding new ways to use DNA to their advantage in the discovery of new species. Often times those new species are plants, and the use of DNA in plants is relatively new, but clearly growing. The field of forensic science is also growing, especially in their knowledge of forensic botany and the many uses of DNA in plant forensics. The use of DNA in plant forensics has been used in death investigation from botanical evidence, helped to create plant DNA databases from trace evidence, as well as creating STR databases to identify drugs that have been seized. In the world of science, DNA will always be used to make advancements, and plant forensics is most certainly a field that is benefiting from them.