Blood Spatter Analysis: Lab Activity



Blood Spatter Analysis: Lab ActivityEstablishing a relationship between Shape and Impact Angle for Blood Stains.How does Impacting Angle Affect the Shape of a Blood Drop?IntroductionAn explosion in media coverage of real crimes, as well as fictitious crime scenes depicted in television dramas has fueled a vast increase in public interest in forensic science techniques. Popular television shows such as “CSI” often depict the forensic scientists as a sort of “jack of all trades”, solving crimes and capturing criminals. In reality, however, these activities fall under the job description of the detectives in charge of the crime. Forensic scientists are highly trained specialists that help collect, analyze, and examine each piece of evidence from the crime scene. Each forensic specialty involves specific techniques requiring a great deal of expertise. One technique used by the crime scene investigators is the analysis of blood stains shed at the crime scene. Blood spatter analysis, or more correctly, “bloodstain pattern analysis” is a powerful forensic tool used in crime scene investigations. If the investigator understands the dynamics of an altercation, how blood behaves when it exits the body, and how it reacts when it contacts a surface, then an attempt can be made to understand what happened and to determine if a crime has occurred.Interpreting the bloodstain patterns involves physical measurement of blood droplets, pattern recognition using known photographs or experiments, the use of trigonometry, and knowledge of the physics of motion. Along with other types of evidence from the crime scene, the forensic investigator pieces together the puzzle to recreate a logical sequence of events, which is supported by the crime scene.MaterialsSimulated bloodMeter stick5x8 note cards (9)Metric calipersNewspaperClipboardTapeOld news papersProcedure: (All blood will be dropped 30 cm from the point of impact)Write your names in the back of each card (lined side).Line your work area with newspapers.Tape one end of the clipboard to the edge of the table by making a hinge out of the tape.Hold the protractor to the edge of the clipboard so that the protractor is perpendicular to the tabletop and aligned so that the center of the protractor is at the edge of the hinged-end of the clipboard.Attach a note card to the clipboard.Select an impact angle from the data table: Example 10 degrees.Set the protractor reading for 90 degrees minus the desired angle. In this example, it will be 90-10 = 80 degrees.From a height of 30 cm drop one drop of blood on to the note card. Allow approximately 5 minutes for drying in position before continuing with the experiment.Measure the length and width of each drop, disregarding the elongated tails of blood, and record in the data table.Repeat steps 5-10 for remaining angles.Blood Spatter Analysis: Lab ActivityEstablishing a relationship between Dropping Height and Blood DiameterHow does Dropping Angle affect the shape of a Blood Drop?Objectives (SWABAT)Establish the relationship between dropping angle and blood drop shape.Recognize patterns around the drop, such as satellite spatter or spines.Develop an understanding of the common types of bloodstain patterns found at a crime scene.Do now Collect your blood specimens from the drying area. Use them to complete your worksheet. Place all dried blood data from the previous experiment in your folder. HomeworkVisit the following URL and examine the photographs of the various categories of blood stains. Choose one category to discuss. You may want to draw diagrams and/or write a paragraph explaining the detailed features of the spatter. ActivityThis is an ongoing activity. For this activity, which should take anywhere from 20-30 minutes, students will be given a handout explaining the materials and procedure. The last 5 minutes of the period will be used to clean up and return the materials to the front of the room. The blood drops will be left on the side table to dry.Data will be summarized during next day’s do now.Exit Slips: How did the drop shape vary with varying angles? NoteThese series of activities will be used to write an in-class report and create standards against which the students will be able to compare from a hypothetical crime scene.The report will be collected and graded using a rubric specifically designed for this work. A hypothetical crime scene will be used as a test at the end of the unit.Students were grouped according to math skills, because these series of activities require some knowledge of basic trigonometry and algebra. While most students, as shown from past activities in the classroom, are able to handle this type of work, 2 groups were identified in which the students need help to get them started and keep them going. These 2 groups were each assigned a student who understands the work well and has the ability to explain to others. Learning standards in Math. Science and TechnologyStandard 1, Standard 2, Standard 4, Standard 6, Standard 7 Blood Spatter Analysis: Lab ActivityEstablishing a relationship between Dropping Height and Blood DiameterHow does Dropping Height affect the diameter of a Blood Drop?Objectives (SWABAT)Establish the relationship between dropping height and blood drop diameter.Recognize patterns around the drop, such as satellite spatter or spines.Develop an understanding of the common types of bloodstain patterns found at a crime scene.Do now Collect your blood specimens from the drying area. Use them to complete your worksheet. Place all dried blood data from the previous experiment in a zip-lock bag and in your folder. HomeworkVisit the following URL and examine the photographs of the various categories of blood stains. Choose one category to discuss. You may want to draw diagrams and/or write a paragraph explaining the detailed features of the spatter. ActivityThis is an ongoing activity. Students are already assigned partners and have a folder with materials.For this activity, which should take anywhere from 20-30 minutes, students will be given a handout explaining the materials and procedure. They will go to the front of the room to get their materials and will set up in the back tables for their experiment. The last 5 minutes of the period will be used to clean up and return the materials to the front of the room. The blood drops will be left on the side table to dry.Data will be summarized during next day’s do now.Exit Slips NoteThese series of activities will be used to write an in-class report and create standards against which the students will be able to compare from a hypothetical crime scene.The report will be collected and graded, while the hypothetical crime scene will be used as a test at the end of the unit. ................
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