Crime scene investigation is a critical step in any criminal investigation. Crime scene investigation begins with surveying a crime scene, identifying potential evidence, photographing potential evidence, processing potential evidence, cataloguing, and collecting evidence. Careful evidence examinations after the scene is processed is a major factor in the ultimate goal of a successful prosecution.
The ultimate end goal is to performed a careful crime scene search, coupled with skilled processing and examining of the collected evidence.
Processing a crime scene can be a very a detailed and tedious process.
Basics of a crime scene search.
1. Securing and protecting crime scenes. One of the most important aspects of securing the crime scene is to preserve the scene with minimal contamination and disturbance of physical evidence. The initial response to an incident shall be expeditious and methodical. Upon arrival, the officer(s) will assess the scene and help any injured victims found, they will also perform a cursory search of the scene for other victims and suspects. The initial responding officer(s) at the scene will conduct an initial assessment and establish control of the crime scene.
2. Obtaining the legal authority to conduct the search of the scene. First responding officers will have made a cursory check of the scene, and they will almost always find evidence during that time. They shouldn’t do more than hold the scene after securing all victims, suspects, and the scene itself. You can perform a search without a warrant if you have voluntary consent; but the search cannot go beyond the consent provided. A warrant to search is issued by a neutral party, (judge) and it’s hard to go wrong with a warrant. A consent search, although easier to get than a warrant is, can cost you later when the person giving consent winds up being the suspect, and they allege the consent was coerced. The 4th amendment tell us :
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”
3. Preliminary walk-though and survey of the scene. The initial responding officer(s) should: brief the investigator(s) who will work the scene; assist in controlling the scene; assist in controlling the scene; and remain on post until released.
4. Locating and marking possible evidence. Evidence shouldn’t be marked until there has been photographs taken without markers, then they can be marked and measure for the sketch, then photographs will be taken.
5. Measuring and preparing rough scene sketches. The roughy sketch is done at the scene with evidence location noted in reference to furniture, walls, etc. Outside scenes will additionally need to have permanent fixtures added so a scene can be reconstructed later using those permanent landmarks to show the location of evidence in needed.
6. Photographing the scene and evidence. Photographs and videos need to be taken before evidence is marked. Photographs need to be taken again after the evidence is marked. Photographs should be taken from far off to show the entire scene, then closer in, and closer still. Lastly, closeups will be made of each piece of evidence. I’ve found that you never take too many photos and you never can take them from too many angles and perspectives.
7. Collecting evidence. The collection and handling of physical evidence is one of the most important factors of the investigation, so take careful steps to package items to avoid contamination and cross-contamination. Establish and maintain proper chain of custody, and prioritize the collection of evidence to prevent loss, destruction, or contamination. Evidence can be recovered bullets, carpet samples and carpet control samples, elimination fingerprints, you name it, it could be important.
Document the collection of evidence by recording its location at the scene, date of collection, who collected it, and always render weapons ‘safe’ and place ‘sharps’ in thick plastic packaging. I’m not going into the process of fingerprinting, processing blood evidence, use of alternative light sources or chemicals in the article, that’s for later.
8.Storing collected evidence. Any bloody evidence that is wet must be collected in paper and the allowed to dry naturally to prevent petrification. Any wet evidence must be dried before final packaging to maintain its integrity as well. Sexual assault evidence kits have to be refrigerated, also refrigerate specimen(s) containing liquid blood; all other biological items should be stored in porous packaging and then kept in storage at room temperature and low humidity – place biohazard warning symbols or labels on biohazard evidence. Different types of evidence require different containers (e.g., porous , nonporous , crushproof) make sure you use the proper method to ensure the integrity of the collected item.
9. Documenting the crime scene and the steps taken in the processing of the scene. A well-documented scene ensures the integrity of the investigation and provides a permanent record for later proceedings.
10. Performing forensic tests and examinations on the collected evidence after the items are brought to the lab. Maintain prior chain of custody records and carefully perform your examination and document what you found. You may be closely checking a collected shoe for minute blood evidence, checking a bedsheet for evidence of a sexual assault with an alternate light source, or you may be fingerprinting items collected at the original scene.
11. Submitting evidence to State, Federal, or private labs for examinations that aren’t handled ‘in-house’. Here, you are continuing a proper chain of custody and submitting an item for testing or examinations that you aren’t prepared to perform. Carefully package the item, and document where the item was sent, how it was sent, and when it was sent.
12. Documenting the examinations you personally performed at your lab. This sometimes is like a second crime scene search as far as documenting goes.
Carefully document what you preformed, and what you found. Lastly, document the disposition of both the original evidence and any new evidence you have collected from it. (Like swabs, or fibers located)
13. Document results received from examinations you sent to other labs. Document what the lab found, and the disposition of the submitted evidence. (You will almost always get your evidence back after it’s been examined.)
14. Prepare a final crime scene sketch. A crime scene sketch records of the size and distance relationship of the crime scene and the physical evidence located and collected there. A sketch is the most simplistic way to present a crime scene layout and measurements to a jury. Sketch programs are plentiful now, and use of one presents a professional sketch for court that shows overall tie-ins to the scene that photographs and videos can’t. A good sketch is a great asset in court. I can’t draw, so if your like me, even a basic sketch program works wonders. Some programs I’ve used are very user friendly but basic, and others are advanced, but they exceed my geek level , so I keep it simple.
Stay with me for future in-depth articles and case studies.