Post 1 (SS): Fibers are a wide range type of evidence. As we move around, fibers are constantly being transferred to people, places and things (Houck, 2015). Fibers are classified as either natural or manufactured. This can help forensic investigators match up fibers to a suspects clothing.The admissibility of all evidence is guided by rules of evidence. The rules of evidence determine what evidence may be admitted, for what uses and under what conditions. The criminal investigation begins when a criminal action begins as a result of activity by the police, prosecutor, or grand jury. Photographs, measurements, witness statements and physical evidence such as firearms, cartridge casings, and bullets found at the scene. Each investigator who handles the evidence must ensure that the chain of custody is maintained and must be able to accurately report on each piece of evidence he or she examines (2009). Forensics become involved in a number of ways such as response to the crime scene and collecting evidence, analysis of the evidence, depositions, and court testimony. Chain of custody is the most important part of handling evidence and presenting it in court. Without the chain of custody or any tampering with this chain, evidence may be thrown out and the qualifications of the forensic investigator may come into question.One challenge that can discredit the evidence is that many types of analysis rely on standard operating procedures meaning that lab reports would be repetitive and unduly consumptive of time (Houck, 2015). Also scientists are called to testify in many situations about methods, procedures, results and conclusions concerning a particular case. If a trial occurs shortly after after the evidence was analyzed, then the scientist should be able to testify directly from memory. There are times that the trial does not occur months or years later and the lab report has to used to memorialize the evidence. The scientist needs to stay within their areas of expertise and not be tempted to answer questions or speculate an answer.Post 2 (JB): At the scene of the hit and run there were tire impression found. The prosecution is trying to convince the court that an 18-year-old female was driving drunk after a party. The woman blew through a red light hitting four college age students. These students were walking across campus. Three were killed instantly, the third did not see anything because of the heavy rain.The prosecutor could do a few things with the impression evidence. Firstly, the prosecutor could use the evidence to tie the womans vehicle to the crime scene. Forensic scientists can determine the make and model of the vehicle based on the impressions that were left behind (Houck & Siegel, 2015, p.90). Tire impressions would make good demonstrative evidence as well. According to the Scientific Working Group for Shoeprint and Tire Tread Evidence (2007) Photographs and casting are one of the first things done when dealing with impression evidence (p.2). The analyst could describe and point out definitive features in the tire impressions. Photographic evidence and a possibility a cast would help construct the crime scene in the minds of the jury. Skid marks could be used to explain how many suspected vehicles were in the intersection at the time of the hit and run.The defense could discredit the evidence by talking about the heavy rain. According to SWGTREAD (2007), the usefulness of impressions can be influenced by environmental conditions, quality, and quantity of evidence. The material used in casting can have an impact (p2). In this case, the evidence and prints would have been affected by the heavy rainfall. If casting material was used whose to say it was not impacted by the conditions. The defense could also talk about who should be considered an expert witness. It would be easy for a forensic scientist to overstep their credibility. Karagioziz (2005) goes into detail about the Wilson vs Woods case. Mr. Rosenhan was an expert in arson reconstruction. He was pulled into this case to reconstruct the scene of a vehicle accident. The court ruled that he was not an expert in this area and thus his testimony was worthless (p.61). Due to legal precedent the same argument could be made on this case.Post 3(BS): An important type of trace evidence is hair evidence. This can be presented as direct evidence, circumstantial evidence, or demonstrative evidence. Direct evidence establishes unreasonable doubt that a person was involved in a crime. This is typically done when DNA is contained within the follicular bulb at the root of the hair (Houck & Siegel, 2015, p. 307). If the follicular bulb is not present on a hair, it may contain circumstantial evidence which suggests a link between a person and a crime scene. Circumstantial evidence is presented in court when the color, shape, treatment, or location of hairs on the body of the suspect match those found at the crime scene (Houck & Siegel, 2015, pp. 301-05). Demonstrative evidence of hairs is presented in court as sketches of the location of hair found within the scene, or photographs of the hair at overall range, midrange, and closeups. Circumstantial evidence is most likely to be discredited in court, and this can be done by pointing out that hairs without DNA only suggest what hair the suspect has, and is not absolutely certain.Footwear impressions can also be demonstrated as direct evidence, circumstantial evidence, and demonstrative evidence. If a shoe is left at the scene of the crime and happens to match the impression, this serves as direct evidence. If a cast is to be taken of the impression, this serves as circumstantial evidence. It may help forensic scientists to determine the shoe size, manufacturer of the shoe, and gait of the owner (Houck & Siegel, 2015, p. 580). This type of evidence will help to suggest a suspect with the same shoe size and ownership of the same type of shoe was possibly present at the scene during the crime. Demonstrative evidence of footwear impressions consist of sketches of the location of the footwear impression within the scene or photographs of the impression with and without a scale in place. Circumstantial evidence may be discredited in court if a cast of the impression does not contain enough unique markings, suggesting there is not a sufficient link that a particular shoe matches that of the suspect’s.Tool mark evidence can be portrayed as direct evidence, circumstantial evidence, and demonstrative evidence. Tools that are left at the scene which match any marks made serve as direct evidence. Tool marks that are cut out of the medium in which they are made also serve as direct evidence. When tool marks in a medium cannot be transported to the lab, casts of the tool marks may also be taken (Pass & Embar-Seddon, 2015, p. 947). Casting of tool marks serves as circumstantial evidence, and may contain striations or unique markings that are similar to those found on a questioned tool. Demonstrative evidence of tool marks may be presented in court as sketches of the location of tool marks within the scene or photographs of the tool marks with and without a scale at overall, midrange, and closeup viewpoints. Unfortunately, if not all striations present in a cast do not match a tool, it will not be accepted as a match, and defense can use this evidentiary standard to discredit any evidence that is not a perfect match (Pass & Embar-Seddon, 2015, p. 947).