When the police first arrive at a crime scene, the entire area must be secured. This means all threats must be eliminated and anyone who needs help should be safely removed. Then the crime scene and all areas that are relevant to the crime scene must be closed off to make sure only authorized personnel can enter. Any authorized personnel who need to enter the crime scene must do so carefully so that they do not tamper with any evidence. At this point, pictures, videos, and sketches should be made in order to document everything about the crime scene before things are moved or cleaned up. Then, trained detectives or forensic scientists should search for and collect any relevant evidence to the crime. Following these guidelines makes a lot of sense, because they preserve as much evidence as possible which is extremely important when trying to solve a crime. It not only gives detectives more evidence to use to reach conclusions, but it also makes sure that the evidence is admissible in the courtroom.  The most important step is to set up an roped off area as quickly as possible. This prevents people from just strolling through the crime scene and destroying evidence. Another important step is to only allow trained professionals to enter the crime scene. These people know the best ways to collect evidence while minimizing the amount of contaminating or tampering of the evidence. Taking these kinds of steps is even more important right now because of all the trace evidence we are able to analyze with recent technology. We are able to pull invisible fingerprints off of an array of different surfaces and we can identify people by the small amount of DNA left in a single drop of spit or strand of hair. The only downside to this kind of evidence is that it is so easy to contaminate or destroy it if the proper steps are not taken. This makes properly securing a crime so important.