IAI CSSA common mistakes
IAI CSSA · Understand the traps and how to avoid them.
Treating 'CSI' as a single role and answering scene-management questions with generic 'secure the scene and call the police' responses instead of distinguishing first responder, scene-of-crime officer, and investigator duties.
Candidates learn the job from television and popular summaries, so they blur who does what and give answers that skip the specific responsibilities of the first officer attending (preservation, log, initial account) versus the SOCO (examination, recovery, continuity).
What to do instead
Build a one-page role matrix before revising: first responder, scene manager, SOCO/forensic practitioner, exhibit officer, investigator, and CSI manager. For each, write the first three actions on arrival. Practise rewriting every generic answer so it names the role performing the action and the point at which responsibility is handed over.
Listing evidence types without explaining the search method, the search pattern chosen, and the reason that pattern fits the scene geometry.
Revision notes tend to be evidence glossaries (fingerprints, DNA, fibres), so candidates can name items but freeze when asked how the scene was searched and why a lane, spiral, grid, or zone search was selected.
What to do instead
For each pattern, memorise one sentence on geometry, one on resource cost, and one on typical scene. Practise short written answers that state: area to be covered, pattern, direction, searchers, markers, and the rationale linked to scene size and contamination risk.
Describing packaging and recovery as 'bag it and label it' without specifying the container, the reason for that container, and the drying or refrigeration requirement.
Candidates memorise that evidence must be preserved but not the material-specific rules, so wet biological items go into sealed plastic, sharp items go into paper, and the answer loses marks on contamination and degradation.
What to do instead
Learn a packaging table by material: wet bloodstained fabric (air-dry, then paper, never sealed wet), DNA swabs (dry, paper, cool storage), sharps (rigid puncture-resistant container), firearms (rigid box, secured, unloaded only by competent person), digital devices (Faraday bag where relevant). Write each answer as container plus reason plus storage condition.
Breaking continuity by omitting the exhibit reference, the time, the location, and the transferring and receiving individuals from the chain-of-custody narrative.
Continuity is taught as a concept rather than as a documentation habit, so candidates describe that a log exists but cannot reproduce the fields that make a chain defensible in court.
What to do instead
Memorise the minimum data set for every transfer: unique exhibit number, description, date and time, location, from whom, to whom, signatures, and reason for movement. Practise writing a five-line continuity entry from a short scenario and check it contains all fields.
Contaminating the scene in the answer itself by moving through it, smoking, eating, using the toilet, or switching lights on and off without recording the change.
Candidates focus on finding evidence and forget that their own actions are part of the scene history; they also underestimate how much alteration of lighting, temperature, and access must be documented.
What to do instead
Adopt a fixed arrival checklist: approach route, entry point, lighting state, persons present, anything moved and why, and who was informed. In practice questions, write the checklist first, then the evidence actions, so contamination control is answered before recovery.
Giving a single definition of a term such as 'primary scene', 'secondary scene', 'transfer', or 'Locard's exchange principle' without applying it to the scenario given.
Definitions are easy to memorise and feel sufficient, so candidates paste them into answers where the question asks for application, losing the analysis marks.
What to do instead
Use a three-sentence structure for every concept answer: define in one line, apply to the facts in one line, state the investigative consequence in one line. Rehearse with paired scenarios (for example a victim found in a vehicle away from the assault location) so the definition is always tied to a decision.
Skipping health and safety and scene risk assessment, or mentioning PPE only as 'wear gloves' without naming the hazard being controlled.
Candidates treat safety as scene-setting preamble rather than an assessed element, and PPE lists are learned without linking each item to blood-borne virus, sharps, chemical, or structural risk.
What to do instead
Write a risk-assessment template: hazard, who is exposed, likelihood and severity, control, residual risk, review point. Map each PPE item to a hazard (double gloves to blood-borne pathogens, FFP3 to airborne particulate, cut-resistant gloves to sharps, helmet and boots to structural). Include dynamic reassessment at each phase.
Confusing identification, individualisation, and reconstruction, and presenting a DNA or fingerprint result as proof of guilt or of the act itself.
Media coverage and case summaries compress forensic findings into 'the DNA matched, so he did it', so candidates overstate what a match establishes and miss the distinction between source attribution and activity-level propositions.
What to do instead
Learn the hierarchy: detection, identification, individualisation, reconstruction. For each evidence type, state what it can and cannot support, and pair it with the alternative propositions (how and when the DNA was deposited). Practise writing conclusions that explicitly separate source-level from activity-level claims.
Ignoring time and resource management in scene strategy, proposing exhaustive examination of every surface regardless of the case, and failing to explain prioritisation or scene release.
Candidates equate thoroughness with maximum collection, so answers never address proportionality, cost, laboratory capacity, or the decision to release a scene and what must be completed before release.
What to do instead
Practise writing a scene strategy with explicit phases: initial assessment, priority examination, targeted recovery, secondary examination, release. For each phase state the objective, the resources, the stopping criterion, and the sign-off. Include a line on what must be documented before release and who authorises it.
Writing report and statement answers as narrative prose with no structure, no exhibit references, and no distinction between observation, opinion, and inference.
Candidates write as they would speak, so statements bury the facts, mix what was seen with what was concluded, and omit the exhibit numbers and times that a court or reviewer needs to follow the account.
What to do instead
Use a fixed statement skeleton: circumstances of attendance, scene condition observed, actions taken with times, exhibits recovered with numbers, persons present, and any limitations. Keep observation sentences factual and put inference in a clearly labelled conclusion. Draft one statement per week under timed conditions and mark it against the skeleton.