When collecting the evidence, it is crucial that cross contamination is avoided at all costs. In order to ensure that the evidence does not get contaminated whilst being collected, the investigator must ensure that all of the collection tools are clean and sterilized and that gloves are changed when handling each different sample. The methods of collection differ depending on the type of evidence and where it is found.
Ideally, evidence should be collected in its original state however evidence that is fragile is easily contaminated or lost. Any transient evidence should be documented in the form of a photograph. The goal of the evidence collection stage in the investigation is to find and preserve any physical evidence that may serve to recreate the crime and find out who committed it, in a way that will stand up in court. Type of Evidence: Biological This type of evidence is photographed so that any blood spatter analysis can still take place if the blood is contaminated.
Any blood that is still in liquid form should be picked up using a sterile cotton cloth and left to dry at room temperature, it should hen be refrigerated and taken to the lab. If the blood is not dry, it should be placed in a container and labeled then it should be placed in a brown paper bag that should also be labeled. If the blood is dry on clothing, the item should be placed in clean paper and then placed in a brown paper bag, it must then be labeled and sealed, it is then subjected to DNA testing.
If the blood stain is present on a small solid object then it is best to place the whole object into a sterile bag, seal and label it and send it to the laboratory. If the blood stain is found on a larger solid object then t is advised to cover the stained areas with clean paper and seal down the edges using tape to prevent contamination ad loss of evidence. Blood is a useful source of evidence as the DNA can help prove that an individual was at the scene of the crime; it can disprove a self-defense claim and can even prove that a certain individual was the one holding the weapon.
A strength of using this method to collect this evidence is that there is little chance of it becoming contaminated as it is swabbed with a sterile swab and placed straight into a sterile container. Another strength of using his method is the material that makes up the end of the swab is effective in holding the blood when it is collected and releasing it when it needs to be tested. This method makes it likely that an individual will be convicted of committing a serious criminal offence.
A weakness of using this method is that the tube contained no preservative and so it may have made the process of testing for DNA more difficult. Another weakness of using this method is that it is controversial and many people believe that keeping an individual’s DNA on a database is a breach of human rights specially when the individual had nothing to do with the crime that was committed. The main concerns are that people may be falsely accused of committing a crime and evidence collection By aquanauts Type of evidence: Chemical This type of evidence is collected and stored in a sterile container, it is then bagged and labeled.
Chemists analyses drugs, paint, explosives, and debris from fire, USSR and soil samples. Chemists are able to test for the presence of any kind of radioactive substances, biological toxins and toxic chemicals. When analyzing evidence from fire berries, it is important that it is stored in a tight and secure container as the any compounds that may be useful will be in an unstable state. A disadvantage of using this method to collect evidence is that if the forensic evidence is not transported in the correct manner, it could result in any detectable traces being destroyed.
Method: In order to determine the type of accelerator used for the fire, the chemist will use a charcoal strip. The strip absorbs the chemical from the debris which are then dissolved in a solvent from which the chemist is able to work out the hydrocarbon intent. An advantage of this method is that it could be used to find out if anything is in the drink left at the crime scene, such as drugs. Chemical analysis of fire debris is very useful as it can help work out the cause of the fire and whether it was an accidental cause.
However, in some cases the evidence is too destroyed and this results in an inability to perform a chemical analysis. Type of Evidence: Physical The investigator performs a visual examination of the body and the surrounding area and takes detailed notes. To estimate the time of death, the temperature of the body ND the room will be measured and recorded. Fingerprints of the victim can be taken at the scene or at the morgue. The investigator takes detailed notes describing the condition of the body and the surrounding area.
After the initial documentation has taken place, the technicians wrap the body up in a white cloth and place paper bags over the hands and feet to ensure safe transportation to the morgue where an autopsy will be carried out to determine the full cause of death. Additional evidence may be collected at this point, such as tissue samples from the victim’s organs, these ill be sent off and analyses at the lab. Impression evidence happens when an object or material takes on the form of a different object from direct contact.
A Judge will accept impression evidence as solid evidence in a trial and once the evidence is collected, impressions are used to find matches. There are three main types of impressions that can be counted as evidence at a crime scene: Footprints Tire tread marks Tool markings By creating electrostatic charges it is possible for the most clean and dry shoes to leave an impression on the ground. A way of collecting and recording these footprint impressions would be to sprinkle fingerprint dusting powder over the recent footprints as this will cause the powder to be attracted to the charge which will create a clear outline of the print.
A disadvantage of using this method is that the residual static charges do not last long and are easily ruined so this method of collecting foot impressions would not be very reliable. Before any attempt is made at collecting a visible footprint left on the ground of a crime scene, photos should be taken using a tripod, level and a ruler. To collect the footprint, a cast should be made out of dental stone. Sprints that are visible on hard flat surfaces can be lifted using fingerprint dust and am electrostatic dust print lifter.
Tire marks left behind at a crime scene can tell the investigators the brand of tire that a criminal had been using. Further inspection of the tire marks can reveal more information, such as any defects that are present of the tire and whether or not the tire has wear due to gravel etc. Tool marks are created at a crime scene when a tool makes contact with an object or a surface and leaves behind an impression. The most common tools used when committing a crime are: Wire cutters Crowbars Screwdrivers These tools may be used to cut and pry away in through windows and doors.
These tools will leave a very distinctive mark that investigators can identify easily. When investigating a crime scene it is highly important to ensure that any evidence is not being contaminated in any way. To make sure that the crime scene is preserved in the correct manner, the investigation team must ensure that very little activity happens in the crime scene and no eating, drinking or smoking takes place near the crime scene. Http://science. Housework’s. Com/CSS. HTML accessed on 25/11/13