High School Forensics: Crime Scene Investigation

• Forensics is the application of scientific methods and techniques to matters of law.
• High school forensics classes provide an introduction to this multidisciplinary field.
• Crime scene investigation is a core component of forensics.

Crime Scene Investigation

• Crime scene investigation involves the systematic processing, documentation, and collection of evidence at the location where a crime occurred.
• The primary goals are to preserve the scene, document its condition, and collect all relevant physical evidence.
• Initial steps include securing the scene to prevent unauthorized access and contamination.
• A thorough walkthrough is conducted to assess the scene and identify potential evidence.
• Detailed documentation involves photography, videography, and sketching to create a visual record of the scene.
• Evidence is carefully collected, labeled, and packaged to maintain its integrity and prevent cross-contamination.
• Chain of custody is a critical aspect, ensuring that the whereabouts of evidence are documented from collection to presentation in court.
• Crime scene investigators work closely with other forensic specialists, such as forensic scientists and medical examiners.
• Proper crime scene investigation is essential for accurate evidence analysis and reconstruction of events.

Evidence Analysis

• Evidence analysis involves the scientific examination of physical evidence to provide objective information about a crime.
• Physical evidence can include a wide range of materials, such as fingerprints, DNA, hair, fibers, blood, weapons, and documents.
• Forensic scientists use various analytical techniques and instruments to analyze evidence.
• Comparison analysis is used to compare evidence samples with known standards or exemplars.
• Identification analysis determines the identity of a substance or material.
• Evidence analysis plays a crucial role in linking suspects to a crime scene, establishing the elements of an offense, and corroborating witness testimony.
• Forensic reports document the findings of evidence analysis and are often presented in court as expert testimony.
• Quality control and quality assurance measures are essential to ensure the accuracy and reliability of evidence analysis.
• Forensic laboratories must adhere to strict protocols and standards to maintain accreditation.
• Forensic scientists specialize in different areas of evidence analysis, such as DNA analysis, ballistics, and trace evidence.

DNA profiling:

• DNA profiling, also known as DNA fingerprinting, is a powerful forensic technique used to identify individuals based on their unique genetic makeup.
• DNA is extracted from biological samples, such as blood, semen, saliva, or hair, and analyzed to create a DNA profile.
• Short tandem repeats (STRs) are commonly used in DNA profiling because they are highly variable among individuals.
• Polymerase chain reaction (PCR) is used to amplify specific STR regions of DNA, allowing for analysis of even small samples.
• The amplified STR fragments are separated and detected using capillary electrophoresis.
• The resulting DNA profile is compared to known DNA profiles in databases or from suspects to identify potential matches.
• DNA profiling has revolutionized forensic science and has been instrumental in solving cold cases and exonerating wrongly convicted individuals.
• The reliability and accuracy of DNA profiling are dependent on proper sample collection, handling, and analysis.
• DNA databases, such as the Combined DNA Index System (CODIS), are used to store and compare DNA profiles for law enforcement purposes.
• Ethical considerations surrounding DNA profiling include privacy concerns and potential for misuse of genetic information.