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DNA Fingerprinting: Its Evidential Value and Limitations in Achieving Justice
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Questions and Answers
Beginning of Forensic Science: Crime Scene Examination, Documentation, and Evidence
1How did crime detection evolve from observation to scientific examination?
- Early detection relied on direct observation of traces, injuries, tools, and documents.
- Photography, measurement, comparison, and laboratory analysis introduced ways to document observations and test hypotheses.
- Every method has limitations: recording the appearance of a trace alone does not establish how or when it originated.
2What have DNA technologies contributed to forensic evidence?
- They allow certain biological traces to be compared with suitable reference samples, supporting or excluding hypotheses about their source.
- Results must be interpreted in light of the sample type, the context in which it was found, and possible mechanisms of transfer.
- The presence of DNA alone does not establish when it was deposited or what activity led to its presence.
3What is a crime scene, and is it limited to one location?
- It is a location or group of locations associated with an incident or with relevant traces, persons, or objects.
- It may include the main room, corridors, vehicles, entry and exit routes, and places where tools were found.
- The scope of examination follows available information and potential evidence and may expand as new findings emerge.
4What is the difference between a physical trace and forensic evidence?
- A physical trace is a material, mark, or alteration observed and documented at a particular location.
- Its evidential value is assessed through examination, comparison, and interpretation in the context of the incident.
- The mere presence of a trace must not be turned into a definitive conclusion about a person or an activity.
5Why is it important to distinguish observation from inference during crime scene examination?
- Observation describes what was actually seen, such as scattered glass beneath a window.
- Inference proposes an explanation for its presence or for the direction of breakage and requires additional findings or tests.
- Keeping the two separate prevents one hypothesis from being treated as fact before alternatives have been tested.
6What are the first responder’s priorities on arrival at a crime scene?
- Saving lives and controlling immediate hazards take priority over preserving traces.
- Assess risks from electricity, chemicals, weapons, and fire, and request specialist assistance when necessary.
- Establish an initial protective perimeter and document changes caused by medical or firefighting intervention.
7How can contamination of a crime scene be minimized?
- Control entry and exit and limit the movement of people and equipment within sensitive areas.
- Change or appropriately clean gloves and tools between samples in accordance with approved procedures.
- Document movements of personnel and equipment and any intervention that could affect interpretation of evidence.
8Why must changes made before the crime scene team arrives be documented?
- Rescue operations may require moving objects, opening doors, or removing obstacles.
- Recording the time, personnel involved, and nature of each change helps distinguish incident-related traces from response-related changes.
- Pass this information to the scene examination lead both verbally and in writing.
9What is the correct sequence for photographing a crime scene?
- Overview photographs first show the location, entrances, exits, and surrounding landmarks.
- Midrange photographs show where the trace lies in relation to furniture, surfaces, and nearby features.
- Close-up photographs record details, using a scale when appropriate, while preserving the original images.
10Why are written notes needed in addition to photographs?
- They record details that may not appear in images, such as odors, lighting, sounds, and timing.
- They document the condition of doors and objects, locations of traces, and procedures performed.
- Record facts in clear descriptive language, distinguishing witness statements from direct observations.
11How should an evidence search method be selected for a crime scene?
- Selection depends on the size and nature of the scene, obstacles, number of examiners, and expected traces.
- Line, grid, zone, or spiral searches may be used depending on the location.
- Document the search area, methods, and limitations; failure to find a trace does not prove its absolute absence.
12What basic precautions should be taken before collecting any crime scene sample?
- Document and photograph the sample’s location, condition, and relationship to surrounding objects before moving it; assign an identifier.
- Consider possible examinations before applying powders or reagents that could affect other traces.
- Use clean tools and appropriate packaging, and record the collector’s identity and collection time.
13How should fingerprints be collected and preserved for examination?
- Begin with visual inspection and assessment of the surface and print condition before choosing a development method.
- Photograph a print suitable for comparison; collect it by an appropriate method or retain the entire item when preferable.
- Protect the print-bearing area from contact and abrasion, and document the detection and recovery methods.
14Why do biological samples require special collection and packaging precautions?
- Samples may deteriorate or become contaminated when shared tools or unsuitable packaging are used.
- Separate samples and manage moisture and storage according to the sample type and laboratory instructions.
- Collect reference and control samples when appropriate to the examination, clearly identifying each one.
15What is the difference between a control sample and a reference sample in forensic examination?
- A reference sample comes from a known source and is used for comparison with the questioned trace.
- A control sample helps evaluate background material, the substrate, or the collection procedure, depending on the examination.
- Package and label them separately to avoid confusion with the evidence sample.
16What should be checked before completing a crime scene examination?
- Review areas examined and those that could not be examined, and confirm that photographs and notes are complete.
- Check that evidence identifiers match across photographs, diagrams, records, and packages.
- Document scene handover, its time, the receiving party, and any remaining hazards or limitations.
17What are the essential elements of a crime scene examination report?
- Incident details, location, dates and times, participants, and relevant conditions.
- Descriptions of observations, procedures, and evidence documented or collected, with references to images, diagrams, and records.
- A clear account of limitations and findings without confusing observations with interpretive opinions.
18What is the chain of custody, and why is it important?
- It is a continuous record of the possession and transfer of an evidence item between people and organizations.
- It records the identities of the receiving and transferring parties, times, purpose, and package or seal condition.
- It helps establish traceability of the evidence but does not, by itself, prove that an examination result was correctly interpreted.
19How does quality management reduce errors in crime scene examination?
- It establishes clear procedures for equipment, packaging, training, documentation, and assignment of responsibilities.
- It uses checklists and independent review without replacing scientific judgment.
- It requires transparent documentation of errors, correction of records, and analysis of underlying causes.
20How does impartial scientific crime scene examination support justice?
- It preserves evidence and its context so that information can be reviewed even after the scene has changed.
- Results may support hypotheses, exclude them, or show that the evidence is insufficient to reach a conclusion.
- It bases evidential weight on evidence, examinations, and their limitations rather than prior assumptions.
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