Blood spatter mini-unit

Analysis of Blood Spatter and

Determination of Point of Origin

Why teach this unit?

This course is designed as an elective course that is also considered as a career pathways class that helps students determine what they would like to focus on in college. In general I teach all of the topics of the class for two main purposes. The first purpose is to make the class as interesting and realistic as possible and the second is to strengthen the science background of students within the class. One of the difficult things to do in science is to apply knowledge to real situations. I am teaching this particular unit to strengthen the conclusion portion of lab write-ups and improve the ability of students to apply knowledge to situations. Additionally, students should also gain an appreciation for the work required for careers in Forensic science.

Audience:

I have designed this unit for my Forensics class at Tualatin High School. This class can fill several requirements for students and thus I have a very diverse population of learners.

1. Career pathway: Students in this category are generally the students that have a major interest in becoming a forensic scientist some day. They generally tend to be fully invested in every activity that I do in class. They may or may not be the highest achieving students in other classes but I can count on them doing very high quality work due to the high level of interest and motivation.

2. General elective: The students that take this class as a general elective have a very diverse ability level. Many of the students that choose Forensics do so because they want to take an interesting class that doesn’t challenge them too much academically. Many of them know me from previous classes and choose the class because they like me as a teacher. They are generally very motivated to do well and put forth maximum effort. Many of them, however fit into the IEP category. They have difficulties in any number of typical school activities and need some form of modification including shortened assignments, alternative test taking, copies of notes, or peer tutors. My forensics classes have the highest percentage of students on IEPs of all of my classes.

3. Science credit: Most of the students taking forensics for science credit are doing so because they have failed in the other science classes they have attempted. They are generally not the most self-motivated and have a lack of confidence in their abilities; they also tend to procrastinate more than most students. They usually have the lowest ability level in reading, math, and overall science lab skills.

4. TAG: I have students that are considered Talented and Gifted in numerous ways and I need to provide a stimulating and rigorous curriculum that meets the needs of those students.

5. ELL: I generally have English Language Learners that fit into any or all of the above categories so it is important that I use vocabulary that does not exclude them from understanding something. It is rare that I have a low level ELL student, however, because this class has only sophomores, juniors, and seniors. I have had to make modifications in the past for some students.

Objectives and Sequencing:

Lesson 1: Introduction to Blood Spatter

Overriding objective: Students will determine the direction of blood spatter with 100% certainty.

I would like to start the unit with an inquiry lab that introduces the idea of blood spatter. Students will be broken up into small groups of 3. Each group member will rotate between an observation recorder, drawer/photographer, and performer of the lab. Each lab group will become familiar with blood spatter by performing labs and making observations at three stations. I will demonstrate what I would like for them to do at each station prior to sending them into the lab.

1. Drip Drop Station: Station one will be a simple set-up of pipettes, simulated blood and butcher paper. Students will be asked to use the pipettes to make blood drops from different heights while keeping some drops separate and allowing some to drip on top of each other. They will be making observations and caliper measurements continually throughout the process.

Psychomotor Objective: After watching the instructor, students will create imitated blood drops using the pipettes.

Cognitive Objective: After performing the lab, students will describe and draw the differences in size and shape of blood drops expelled from the dropper.

Cognitive Objective: After completing this activity, students will describe what a blood drop looks like when dropped from 90 degrees, or straight down.

2. Blood Spray Station: Station two will get messy! The set-up will include paintbrushes, simulated blood and butcher paper. Students will be asked to dip the brush in the blood and swing away at several different velocities…slow, medium, and fast. They will be making observations continually throughout the process.

Psychomotor Objective: After watching the instructor, students will create imitated blood spatter using the brushes

Cognitive Objective: After completing the lab, students will draw the differences in size and shape of blood drops released at different velocities.

Cognitive Objective: After completing the lab, students will describe the differences in size and shape of blood drops released at different velocities.

Cognitive Objective: After performing the activity, students will draw the shapes of blood drops moving from left to right and right to left.

Cognitive Objective: After performing the activity, students will describe the shapes of blood drops moving from left to right and right to left.

3. Splat and Splash Station: The final station will have a set-up of pie plates filled with simulate blood and some different utensils used to smack down into them…they will be enclosed in some type of box with three sides to catch all the spatter directions. The actual utensils need to be researched a bit first but I am thinking a spatula, wooden spoon, and the flat side of a meat tenderizer.

Psychomotor Objective: After watching the instructor, students will create imitated blood spatter of blunt force trauma.

Cognitive Objective: After completing the lab, students will describe and draw the differences in size and shape of blood drops they see along the sides of the enclosure.

Once they are finished with the lab and the clean-up, I will bring them back together and ask them to graph the information from station 1 and discuss the effects of height, velocity, and direction on blood drops. Each group will then pair up with another group and discuss their findings. They will be asked to add additional observations and information to each lab if it is needed. I will then show a short PowerPoint describing the observations I made and how the observations relate to the objective.

Homework: The small groups will write a collaborative conclusion describing the effects of height, velocity, and direction on blood drops using Google docs.

Lesson 2: Determining Impact Angle of Blood Drops

Overriding Objective: Students will determine the angle of impact of a blood drop within 5 degrees.

For this objective I will demo the lab set-up, which will be a piece of cardboard, covered with butcher paper and taped to the lab station. Students will use a protractor to lift the board at certain angles. They will then drop simulated blood onto the board with a pipette and measure it. The data will include the actual angle, the drop length, and the drop width. Students will measure drops from 90o through 0o using the protractor as a guide. Students will then calculate the angle based on the measurement they attained using the width divided by the length and applying the resulting decimal to a sin table (they can also use a calculator if they would like). Students will write a conclusion to compare the calculated angle with the measured angle and determine the percent error involved.

Psychomotor Objective: After setting up the lab, students will accurately recreate simulated angles using the lab set-up and a protractor.

Psychomotor Objective: After dropping simulated blood, students will accurately measure the length and width of blood drops within a range of 1 millimeter (+ or – 1) in order to determine the angle of impact.

Cognitive Objective: After taking measurements, students will apply the following mathematical relationship: angle = arc sin [drop width/drop length] using either a calculator or a sin table.

Cognitive Objective: After applying the mathematical relationship, students will compare the actual measured angle to the predicted mathematical angle and discuss any discrepancies using logical analysis.

Homework: Finish conclusion and error analysis

Lesson 3: Determining the Point of Origin of an Attack

Overriding Objective: Students will apply the principles of blood spatter to determine the point of origin of an attack with 10% error or less.

I will start this objective by demonstrating how to run a string from a blood drop using my measurements, a sin table, a string, tape, and a protractor.

In the final lab for the unit I will set up stations with predetermined angles and points of origin. Students will have to use the knowledge learned from previous labs, discussions and demonstrations to determine the direction of the blood spatter, the angle of impact of the drops, and ultimately the point of origin. They will measure the height from the ground and distance from the wall for the point of origin and take a photograph of the intersecting strings. I will assess them based on the accuracy of their determined point of origin.

Cognitive Objective: Using a pre-made, mock crime scene, students will apply knowledge to determine the angle of impact of 6 blood drops.

Psychomotor Objective: After the demonstration, students will accurately “string up” a mock crime scene to determine the point of origin of an attack within 10% error.

Affective Objective: Students will describe the importance of teamwork in this lab and relate it to the professional world of Forensics.

Evaluation of Instruction:

As with most labs in science I think there are two major possibilities for struggle in these activities. The first struggle generally comes with the application of ideas. I will try to alleviate those issues by doing thorough demos and allowing time for practice in small groups. I will walk around for further instruction as well. The second issue generally comes in the summary of concepts. This is an issue that has many points of origin such as a lack of writing ability or, in some cases, a total lack of understanding of the topic. I anticipate a wide variety of within the summary of information, but I think that I can use the other parts of my assessment to observe whether or not learning is taking place.

Blood Spatter Rubric

CATEGORY 4 3 2 1

Recreating Blood drops N/A N/A

Drops are clear and accurate and make the analysis easier to understand.

Drops are inaccurate and do not facilitate analysis

Analysis and Description of Drops

A description is made and the relationship between the variables is discussed and trends/patterns logically analyzed.

A description is made and the relationship between the variables is discussed but there is no analysis of patterns or trends based on the observations.

A description is made but there is no analysis of the relationship between the variables, patterns or trends based on the observations.

A very simple description is given.

Drawings of Spatter Straight Down

Clear, accurate drawings are included and make the analysis easier to understand. Drawings are labeled neatly and accurately.

Drawings are accurate and are labeled neatly.

Drawings are included and accurate but not labeled.

Drawings are present but inaccurate

Recreating Blood Spatter N/A N/A

Spatter is accurate and makes the analysis easier to understand.

Spatter is inaccurate and does not facilitate analysis

Drawings of Spatter at Different Velocities





Description of Spatter at Different Velocities





Drawings of Spatter in a Given Direction





Description of Spatter in a Given Direction





Recreation of Blunt Force Trauma Spatter

N/A N/ADrawings are included and accurate but not labeled.


Recreating Angles N/A N/A

Angles are accurate and make the analysis easier to understand.

Angles are inaccurate.

Blood Drop Measurements

Measurements are accurate within .01 cm.



Measurements are inaccurate

Mathematical Calculations

All calculations are shown and the results are correct and labeled appropriately.

Some calculations are shown and the results are correct and labeled appropriately.

Some calculations are shown and the results labeled appropriately.

No calculations are shown OR results are inaccurate or mislabeled.

Determination of Drop Angles N/A N/A

Angles are accurately measured within 5 degrees

Angles are measured but

String-up of Lab

Illustrates an accurate and thorough understanding of scientific concepts underlying the lab.

Illustrates an accurate understanding of most scientific concepts underlying the lab.

Illustrates a limited understanding of scientific concepts underlying the lab.

Illustrates inaccurate understanding of scientific concepts underlying the lab.

Summary

Summary describes the skills learned, the information learned and some future applications to real life situations including the importance of teamwork

Summary describes the information learned and a possible application to a real life situation.

Summary describes the information learned.

Only an arbitrary summary is written and not much is described

Blood spatter mini-unit

Education

Transcript of Blood spatter mini-unit