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→ Fundamentals of Crime Scene Investigation
John Calvin Gaziano is a blood spatter expert with over 27 years of law enforcement experience, 20 of which were in the crime scene unit. He has been certified as a bloodstain pattern analyst by the International Association for Identification (IAI) since 2009 and as a senior crime scene analyst since 2015. In addition, he also holds a homicide investigation certificate of achievement from the Robert Presley Institute of Criminal Investigation (ICI). John is currently the only IAI-certified bloodstain pattern analyst in Texas.
John worked in the Crime Scene Investigation Unit of the Fremont Police Department for over 20 of his more than 27 years and retired in 2021. He was the Sergeant (supervisor) of the crime scene unit during the latter portion of his career. During this time, he processed, analyzed, and reconstructed thousands of crime scenes. His training consists of thousands of hours in bloodstain pattern analysis and crime scene investigation. As a blood spatter expert, he consults and testifies in court proceedings.
John received a Master of Forensic Science Degree from National University and a Master of Science degree from San Jose State University. He also holds a Bachelor of Science Degree from the University of California, Berkeley.
John has lectured as a bloodstain pattern analyst at more than 100 conferences and forensic science groups across the United States. He has been consulting and providing crime scene training since 2011. John teaches 40-hour crime scene investigation forensic training courses, which include bloodstain pattern analysis and crime scene photography. He plans to offer additional courses in the future.
As a crime scene and blood spatter expert, John has three written materials on bloodstain pattern analysis. One of his published works and contributions to the discipline, Crime Scene Photography, was published in 2016 and features a section on bloodstain pattern analysis photography and documentation. He wrote a manual for his 40-hour bloodstain pattern course titled Bloodstain Pattern Analysis: An Investigative Approach (2011) and his college thesis titled Reconstruction of Bloodstain Impact Patterns: Error Rates (2017).
Bloodstain pattern analysis is a discipline within the field of forensic science. During a violent incident, blood is deposited on various surfaces, and the aftermath is interpreted by crime scene personnel. A bloodstain pattern analyst can reconstruct events during an incident by analyzing bloodstain patterns and stains. An analyst can determine the following:
At Gaziano Forensic Consulting, we use the scientific method to ensure that our experiments are conducted in a controlled and reproducible manner. This allows us to generate accurate results that can be relied upon in court proceedings.
The scientific method is an inquiry process that allows scientists to understand the natural world better. The scientific method tests hypotheses, which are educated guesses about the outcome or answer to a problem. A hypothesis states that a particular result can be expected if specific variables are introduced.
Bloodstain pattern analysts use the scientific method to bloodstain patterns at crime scenes. They begin with an observation, which leads to a question. A hypothesis is formed based on the question. The hypothesis is tested through experimentation, and the experiment results are analyzed. The bloodstain pattern analyst either supports or rejects the hypothesis based on the experiment’s results. This process is essential in bloodstain pattern analysis, as it helps ensure that conclusions are based on evidence, not simply on guesswork.
The bloodstain pattern analyst often performs experiments to help resolve issues and determine the most probable events during an incident. Furthermore, the analyst should be objective and control for variables when performing experiments.
When reconstructing events at a crime scene, the analyst gathers information to 1) assist in ruling out specific hypotheses and 2) determine the most probable scenario. Analysts can never know if the reconstruction of events is 100% accurate; however, by applying the scientific method and using the information gathered from the crime scene, they can identify the most probable sequence of events. By applying the scientific method, analysts can maintain objectivity and reach a conclusion.
Reconstruction of the events during an incident requires that the gathered information be used to eliminate the impossible and focus on the most likely scenarios. Using the scientific method eventually leads to identifying the most probable sequence of events that occurred during the commission of a crime. This includes the examination of all physical evidence, police reports, lab reports, pathology reports, witness statements, photographs, and other documents associated with the case.
The scientific method has been used in many different scientific disciplines. Bloodstain pattern analysis follows the principles of biology, mathematics, physics, and chemistry. Proper use of the scientific method should guide analysts to their conclusions.
Although the scientific method has been documented extensively, with variations in the number of steps used to reach a conclusion, we put forth a 5-step process as the various established methods all include the same general concepts.
The first step in using the scientific method is to determine the problem. To do this, the analyst must clearly understand what information is needed. The problem should be specific and focused so that it can be resolved.
Gathering information is the second step. This includes anything that pertains to the case, such as medical reports, physical evidence, photographs, crime scene reports, testimonial evidence, etc. The analyst should get all relevant information before moving on to the next step.
The third step is to form a hypothesis. A hypothesis is an educated guess as to the outcome or answer to the problem. A hypothesis states that a particular result can be expected if specific variables are introduced. The analyst should use deductive reasoning when forming the hypothesis.
The fourth step is to test the hypothesis. This is done by performing experiments. The experiments should be designed to control for variables so that the results are accurate.
The fifth and final step is to analyze the results of the experiments and form a conclusion. The analyst should be objective when analyzing the results. If the results support the hypothesis, the analyst can conclude that the hypothesis is correct. If the results do not support the hypothesis, then the analyst should modify the hypothesis and repeat the process.
The scientific method is a process that has been used for centuries to help scientists determine the most probable sequence of events. This involves gathering information, formulating a hypothesis, testing the hypothesis, and analyzing the results. Bloodstain pattern analysts can maintain objectivity and reach a conclusion using the scientific method.