Read My Lips: Lip Print Analysis
Lesson 11 of 15
Objective: SWBAT practice the forensic techniques of print comparison and paper chromatography.
You will need to provide the following materials for this lab:
- Lipstick (3 different brands, all the same color) To save money, you may wish to buy 2-3 set of tubes and ask student groups to share.
- Filter paper in large enough pieces to cut 8” by 1/2” strips. (4 strips per student group)
- Small glass beakers (25 or 50 ml)
- Glass graduated cylinders (50 or 100ml)
- Acetone (available at most hardware stores)
- Rubbing alcohol (70% isopropanol)
- Metric rulers
- Dissecting microscopes or hand lenses
- Q-tips (1-2 per student)
You will need to set-up the following materials prior to lab:
- Label the lipstick tubes A, B, and C. If you are using multiple sets, make sure each set labeled the same.
- Prepare a solution of 50% acetone and 50% rubbing alcohol. Store in sealed, labeled, glass containers. NOTE: Acetone produces unpleasant, noxious fumes. Use in a well-ventilated area or under a hood. Both acetone and rubbing alcohol are flammable.
- Prepare an envelope containing a sample of the lipstick found at the scene of the crime. This envelope should contain one 8” by 1/2” strip of filter paper with a line of lipstick drawn 2 cm from one end. The lipstick used to make this mark should be labeled “C”.
- Prepare an envelope containing a partial lip print on a paper surface. To make this lip print, you or another person should apply lipstick to your lips and press your lips to a small square of white paper. Cut-out a small piece of the lip print and place it in the envelope. Discard the remaining part of the print.
- Prepare three envelopes containing lip prints of each of the suspects on paper (marked "Suspect 1", "Suspect 2", and "Suspect 3"). Follow instructions above for making lip prints, except do not cut the prints. The lip print that goes in envelope 3 should be from the same person as the evidence print above. The other two prints should be from different people. Try to get people with very different lip shapes and/or sizes.
Use the following key to check how each lipstick or envelope should be labeled.
- Suspect 1 = non-matching suspect
- Suspect 2 = non-matching suspect
- Suspect 3 = matching suspect
- Lipstick A = used by non-matching suspect
- Lipstick B = used by matching suspect
- Lipstick C = used by non-matching suspect
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?"
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
Next, I pass out the Student Lip Print Lab and have the students read through the directions with their table groups. After the first reading, I would ask the students to paraphrase the procedures for both parts 1 and 2. Understandably, they will not be able to describe all of the steps in a way that is detailed enough to actually implement it. However, it will give them an overall idea of what is expected in this lab. We discuss the process, including how long the lab will take, what materials would be needed, etc.
Next, the students reread the lab, highlighting details that they will need to focus on when implementing the lab. I call on random students to share a few things they highlighted, asking the class to raise their hands if they also highlighted that specific step, sentence, or phrase. If a large number of students have their hands raised, this will signify to others that they should probably pay more focus to this specific part of the lab. We discuss this in quite depth, as the students will be responsible for understanding and following the procedures carefully without much guidance from me. Since I teach this unit later in the year after we have had many lab experiences, I feel students are at the point where they should be able to read and follow the directions written in a science lab. I have them grouped heterogeneously so that they can support each other, but I try to step away from reading or paraphrasing simple procedures and focusing more on posing clarifying or deeper level questions to groups of students as they perform labs. I feel this is a more useful way to facilitate discussion, reflection, and learning as students work in class.
Once students have read through the lab twice and highlighted the important ideas to keep in mind while performing the lab, I set them to work. As usual, I incorporate lab roles (from Ms. Sanchez's Class) to encourage students to both take accountability and work cooperatively during the lab activities. This provides structure to the classroom and ensures all students are involved in the learning tasks.
After completing the Day 2 portion of the lab, I have students jigsaw with members from other groups, forming new groups of 4 students. In these new groups, they each share the results of their Lipstick Chemical Analysis Data Sheet. They will compare the data they collected for accuracy. If they feel that they got very different results from another group, they will consult 2-3 people from other groups and compare to their results, so that they can determine which is the most accurate.
Once each group fees they have the most accurate data, they will work together (still in their new groups) to determine the suspect, based on the lip print and the type of lipstick that was used.
After students have finished, they may use Q-tips to collect some lipstick from the tube and place it on their lips to practice making and comparing their own lip prints to those of their teammates.
Students will easily be able to create and analyze their lip prints, but it is almost inevitable that someone will ask, "What if the suspect is a guy? They don't wear lipstick." To help them understand how to get lip prints from someone who may not wear lipstick, I play the Lip Prints video:
After watching the video, I ask students to consider what might be left behind if the suspect is not wearing lipstick or lip balm, as shown in the video. After giving some think time, I explain that lip prints can also be recorded by:
- Photographing the suspect′s lips.
- On a non-porous flat surface such as a mirror they can be photographed, enlarged and overlay tracings made of the grooves.
- Applying lipstick, lip rouge, or other suitable transfer mediums to the lips and then having the individual press his or her lips to a piece of paper or cellophane tape or similar surface.
- Using a finger printer, preferably a roller finger printer.
- By having the subject impress his or her lips (without lipstick or other recording medium) against a suitable surface and then processing these prints with either conventional finger print developing powder and brush (as shown in the video above).
Hopefully, students will be able to draw upon the knowledge they have gained in the last few lessons and suggest that DNA from skin cells on the lip could be left on anything that the suspect has placed his/her mouth on. In this case, DNA can be compared to samples and analyzed to see if there is a match to a suspect or victim.
As a final evaluation of the lesson, I ask each student to use their laptop's webcam to record a verbal reflection that addresses the following questions:
- Who did you identify as correct suspect? What evidence did you find to prove it?
- Which lipstick was the suspect wearing at the crime scene? What evidence did you find to prove it?
- What were the toughest parts of analyzing lip prints?
- How can you see this used at a real crime scene? Provide an example.
They record their webcasts and send them to me via email. I will assess their understanding through the use of proper terminology, the accuracy of their responses, and the quality and comprehension of their responses.