MLT GlobeForensic Science: Evidence handling & chain of custody – page 2
30 Forensic Science MCQs on Evidence handling & chain of custody with answers and explanations.
Liquid blood tubes collected as DNA reference samples are awaiting transport. How should they be kept?
Refrigeration slows degradation of liquid blood. Freezing glass tubes risks breakage, heat degrades DNA, and discarding cells removes the nucleated leukocytes needed for DNA.
Under ISO/IEC 17025, which of the following must a test report include?
Reports must identify the item, the method used, the results with units, relevant limitations, and the authorised person. This allows the result to be understood and reviewed.
What is the proper role of a laboratory scientist testifying as an expert witness?
The expert's duty is to the court. Opinions must be objective, based on the evidence and methods, and limited to the witness's area of competence.
An unknown DNA profile at a scene matches a first-responding officer. Which practice is designed to recognize such cases?
Elimination databases of investigators, scene staff and laboratory personnel allow profiles introduced during legitimate handling to be recognised and excluded, preventing false leads.
Which international standard specifies general requirements for the competence of testing and calibration laboratories, including forensic laboratories?
ISO/IEC 17025 covers technical competence and impartiality of testing laboratories and is the basis for forensic laboratory accreditation. ISO 15189 is for medical laboratories.
What is the primary purpose of external proficiency testing in an accredited forensic laboratory?
Proficiency tests are samples of undisclosed composition from an external provider. Results demonstrate ongoing competence and are required by accreditation standards.
An analyst makes an error in handwritten bench notes. What is the correct way to correct it?
Original entries must remain legible. A single strike-through with initials and date keeps the record transparent and preserves its integrity for review and court.
Under the Daubert standard for admitting scientific evidence, which factor is considered by the court?
Daubert factors include testability, peer review and publication, known or potential error rate, existence of standards, and general acceptance in the scientific community.
Which practice reduces cognitive bias when interpreting a DNA mixture?
Linear sequential unmasking requires the evidence profile to be interpreted and documented first. Knowing the reference profile beforehand could unconsciously influence allele calls.
DNA testing will consume the entire limited stain on an exhibit. What is good practice before testing?
Consumptive testing prevents independent retesting. Laboratories typically obtain approval from the submitting agency, which allows the defence to be notified or to observe.