Forensic Laboratory Procedures Flashcards

What is the first step in forensic laboratory evidence processing?

Answer: Receiving and documenting evidence

The first and most critical step in forensic laboratory evidence processing is the proper receiving and meticulous documentation of all submitted evidence. This initial step establishes the integrity of the chain of custody, accurately records what was received, and prevents any disputes about the evidence's origin or handling. Without this foundational step, subsequent analyses could be compromised, and the admissibility of evidence in court could be challenged.

Why is chain of custody important in forensic labs?

Answer: Maintain evidence integrity

Chain of custody is paramount in forensic labs to maintain the integrity and authenticity of evidence. It involves a meticulously documented chronological history of evidence, detailing its collection, seizure, custody, control, transfer, analysis, and disposition. A robust chain of custody ensures that evidence has not been tampered with or contaminated, which is essential for its admissibility and credibility in court.

What is the purpose of DNA quantitation in the lab?

Answer: Measure DNA amount

The purpose of DNA quantitation in the lab is to accurately measure the amount of human DNA present in a forensic sample. This measurement is a vital step before DNA amplification, as it ensures that the optimal amount of DNA is used for subsequent reactions. Proper quantitation helps prevent issues like PCR inhibition or preferential amplification, leading to more reliable and interpretable DNA profiles.

How is contamination prevented in forensic labs?

Answer: Use clean workspaces and protocols

Contamination in forensic labs is rigorously prevented through strict adherence to protocols, including the use of clean, designated workspaces, sterile equipment, and personal protective equipment. Separating samples, maintaining one-way workflows, and regular decontamination of surfaces also minimize the risk of transferring foreign DNA. These measures are critical to ensure the integrity of evidence and prevent false or misleading results in forensic investigations.

What equipment is essential for PCR in forensic labs?

Answer: Thermocycler

A thermocycler is the essential piece of equipment for Polymerase Chain Reaction (PCR) in forensic labs. It precisely controls the rapid heating and cooling cycles required for DNA denaturation, primer annealing, and DNA extension, which are the core steps of PCR. Without a thermocycler, the amplification of specific DNA segments, crucial for generating sufficient DNA from crime scene samples for forensic analysis, would not be possible.

Why is documentation critical in forensic labs?

Answer: Ensure traceability and validity

Documentation is critically important in forensic labs to ensure the traceability and validity of all procedures, results, and evidence handling. Meticulous records provide a complete audit trail, allowing for the reconstruction of analyses, verification of methods, and demonstration of compliance with quality standards. This thorough record-keeping is essential for maintaining the integrity of evidence and its admissibility in legal proceedings.

What is electrophoresis used for in forensic analysis?

Answer: Separating DNA fragments

Electrophoresis is a fundamental technique in forensic analysis used to separate DNA fragments based on their size. After DNA amplification, such as PCR of STRs, the resulting fragments are loaded into a gel or capillary, and an electric current is applied. This process allows scientists to visualize and differentiate DNA fragments, which is crucial for creating a unique DNA profile for individual identification in forensic investigations.

What is the importance of calibration in forensic lab equipment?

Answer: Ensure reliable results

Calibration is crucial in forensic labs because it ensures that all equipment provides accurate and precise measurements. This process verifies that instruments are functioning within specified parameters, which is essential for generating reliable and trustworthy results that can withstand scrutiny in a court of law.

How are quality controls used in forensic labs?

Answer: Verify valid results

Quality controls are indispensable in forensic labs to verify the validity and reliability of testing results. By including known positive and negative samples, labs can confirm that the analytical methods are working correctly, detect potential contamination, and ensure the accuracy of the unknown samples being tested.