Teacher Notes
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Teacher Notes![]() Examining Evidence Using Fingerprint AnalysisStudent Laboratory KitMaterials Included In Kit
Isopropyl alcohol, 28%, 250 mL
Cotton balls, 50 Inkpads, 6 Evidence Fingerprint Cards, 2 Suspect Fingerprint Cards, 30 Additional Materials Required
Practice paper
Soap and water Prelab Preparation
Safety PrecautionsIsopropyl alcohol is a moderate fire risk as it is a flammable liquid. It is also slightly toxic by ingestion and inhalation. Wear chemical splash goggles. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information. DisposalPlease consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Used cotton balls and Fingerprint Records may be discarded in the regular trash according to Flinn Suggested Disposal Method #26a. Remaining isopropyl alcohol may be saved for future use or disposed of according to Flinn Suggested Disposal Method #18a. Lab Hints
Correlation to Next Generation Science Standards (NGSS)†Science & Engineering PracticesPlanning and carrying out investigationsAnalyzing and interpreting data Using mathematics and computational thinking Engaging in argument from evidence Disciplinary Core IdeasMS-LS1.A: Structure and FunctionHS-LS1.A: Structure and Function Crosscutting ConceptsPatternsStructure and function Performance ExpectationsHS-LS3-1. Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring. Sample Data(Student answers will vary.) Answers to Questions
Teacher HandoutsReferencesFederal Bureau of Investigation. Fingerprint Identification. http://www.fbi.gov/hq/cjisd/ident.pdf (accessed January 22, 2010). Recommended Products
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Student Pages
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Student Pages![]() Examining Evidence Using Fingerprint AnalysisIntroductionThe fingerprint continues to be one of the most important and valuable pieces of forensic evidence. Fingerprints are unique for each person. There are even slight differences in the fingerprints of identical twins. By comparing fingerprints at a crime scene with a suspect’s fingerprint record, officials can establish a person’s presence at a particular location. Concepts
BackgroundHuman skin represents the body’s first line of defense against foreign invasion and infection (see Figure 1). Skin is composed of an epidermal outer layer and a dermal inner layer. The surface between the epidermis and dermis is usually uneven, because the epidermis has ridges projecting inward and the dermis has finger-like papillae passing into the spaces between the ridges. This uneven boundary area is what contains the friction ridge structures responsible for our one-of-a-kind fingerprint patterns. These ridge patterns begin to form in the eighth gestational week and remain unchanged throughout an individual’s life. Typically, the only changes that occur thereafter are due to scar tissue. {10994_Background_Figure_1_Human skin cross section}
Sweat glands are located in the dermis and their ducts extend up through the epidermis, where they release perspiration, oils and other materials through sweat pores. The perspiration, oils and salts from these sweat glands leave an identifiable residue conforming to the pattern of an individual’s fingerprints. The human population has three main fingerprint patterns, each with various subgroups. {10994_Background_Table_1}
A loop pattern has one or more ridges entering from one side, curving, and then leaving the same side it began, as illustrated in Figure 2—(1) Ridge Ending, (2) Bifurcation, (3) Enclosure, (4) Short Ridge, (5) Dot (Island). Loop patterns always develop ridges that diverge to form a delta. It resembles a “Y” pattern. All loops must have one delta.
{10994_Background_Figure_2_Loop pattern with ridge characteristics}
A loop pattern on a fingerprint card that opens toward the thumb is a radial loop. A loop pattern that opens opposite the thumb is an ulnar loop, as shown in Figure 3. Remember, a fingerprint record is a mirror image of the actual fingerprint.
{10994_Background_Figure_3_Ulnar and radial loop patterns on a left hand}
Whorls are friction ridge patterns that have a minimum of two deltas as illustrated in Figure 4. There are four whorl subgroups: plain, central pocket, double loop and accidental.
{10994_Background_Figure_4_Plain and central pocket whorl patterns}
The plain whorl has two deltas and a complete ridge circuit. It is almost a “circular” pattern. The central pocket whorl differs from the plain whorl in one of the delta areas shown in Figure 4. The deltas are not symmetric and one side appears to be stretched like elastic (shown by the smaller circle). The double loop whorl (see Figure 5) is composed of two loops and two deltas. The last whorl subgroup is the accidental (Figure 5). This pattern is defined as a “pattern consisting of a combination of two different types of patterns, with the exception of the plain arch with two or more deltas or a pattern which possesses some of the requirements for two or more different types or a pattern which conforms to none of the definitions.” {10994_Background_Figure_5_Double loop and accidental whorl patterns}
Arches (see Figure 6) are friction ridges that enter on one side of the finger and cross to the other side rising upward in the middle. The simplest is the plain with mild bulging. The tented arch appears to have a spike acting as the pole in the middle.
{10994_Background_Figure_6_Arch patterns}
Fingerprints are processed through the Integrated Automated Fingerprint Identification System (IAFIS). The fingerprints are submitted electronically or by mail, processed by IAFIS, and a response is returned to the contributing agency within two hours or less for electronic criminal fingerprint submissions and 24 hours or less for electronic civil fingerprint submissions. Fingerprint processing has been greatly expedited with the implementation of IAFIS.
Experiment OverviewThe purpose of this activity is to make a card with your fingerprints. Each class member will compare the fingerprints obtained for two individuals on the Evidence Fingerprint Record from a simulated crime scene to the fingerprints of up to 30 possible suspects in the classroom. Examine the evidence against each suspect to confirm the criminals’ identity. Materials
Isopropyl alcohol, 28%, < 1 mL
Cotton ball Evidence Fingerprint Record Ink pad (shared) Practice paper Soap and water Suspect Fingerprint Card Safety PrecautionsIsopropyl alcohol is a moderate fire risk as it is a flammable liquid. It is also slightly toxic by ingestion and inhalation. Wear chemical splash goggles. If ink contacts clothing, rinse immediately to prevent the stain from setting. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines. ProcedureNote: Obtaining clear, high-quality inked fingerprints takes practice. Pressing too hard or using too much ink may smear the fingerprint.
Student Worksheet PDF |