Bloodstain Analysis

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Objective

SWBAT understand how bloodstain analysis is conducted in the field of forensics. SWBAT describe the factors that can affect the formation blood stains and splatters at a crime scene.

Big Idea

The presence of blood can tell us a great deal about when, where, and how a crime occurred. Students will analyze a series of blood stains to investigate the details of a crime.

Engage

5 minutes

 

I start each class period in this unit with a warm-up activity that targets forensic science concepts and other skills (observation, problem-solving, etc.) Not only does this get the students in the frame of mind necessary to address the field of forensics, but it also introduces key vocabulary they will use throughout the unit in a more relevant way. In addition, this activity allows students to refine their research skills as they perform quick internet searches to find the correct answers. By using the attached weekly Answer Sheet* and passing it out as they enter the classroom every Monday morning, not only can I save paper, but I can also provide a routine that allows students to begin without prompting, waiting for paper, or asking things such as, "What do we do?" and, "Where do we write our answers?"

For this particular lesson, I have decided to utilize a Trivia Challenge*, in which students use their knowledge of forensics and their research skills to answer an assortment of trivia questions.

After providing about 2-3 minutes to look for the answers, we go over them together and discuss the information provided. I help students to define key terms and providing background knowledge necessary to help students understand the questions. However, I do not spend as extended period of time on this portion, as it is just meant to be an activator and not necessary to understanding the core of the lesson at this time.

*Challenges and answer sheet courtesy of http://sciencespot.net/Pages/classforscistarters.html

Explore

30 minutes

I start this portion of the lesson by having the students form groups of three and give each group a copy of the Bloodstain Analysis Introduction, as well as copies of one of the pages from the Bloodstain Analysis article. We start by reading the introduction together as a class, in order to help provide a framework for today's lesson.

After reading the introduction, I use the Jigsaw Reading strategy. I explain that each student reads their page from the article independently, and then reread in their group of three. Once they have read and discussed the page they have been given, they work together to create a poster to illustrate the main points of their page.

Explain

10 minutes

After creating their poster, each triad shares them with the rest of the class, explaining their drawings and their significance to the article. I have groups that were assigned the same page share one after the other, so that we can compare each group's perspective on the same material and ask questions. This will allow them to collaborate to answer the questions and share information.

Elaborate

30 minutes

In order to learn more about how the appearance of a bloodstain results from a variety of factors, students will now complete the blood splatter lab. Students love this lab, as it includes that "gross factor". I prepare the fake blood ahead of time (instructions are included in the lab), but I find that I never have enough on hand and often have to make more during the lab.

I like to pretend the kids are working with real blood - even though they always know better - and I don't like to give away the ingredients in the fake blood, so this ruins the sense of mystery I like to put on. If you want to work smarter and not harder, stock up on fake blood during the Halloween season and save it for this activity!

The lab is written with very clear directions for students to follow on their own. While they are working, I circulate through the room, mainly to make sure the gross factor doesn't get students too carried away and to keep them focused on the objectives of the lab.

Evaluate

20 minutes

Students demonstrate their learning by completing the bloodstain analysis simulation with a partner of their choosing. This simulation requires them to step into the shoes of an investigator and view several images from a crime scene* to determine the details of the crime.

Prior to completing the analysis, they read through the tutorial in order to become familiar with the terminology and processes involved in the simulation. Students compare their analysis with the results and explanations given at the end of the simulation.