NCA Evidence common mistakes
NCA Evidence · Understand the traps and how to avoid them.
Treating 'beyond reasonable doubt' and 'balance of probabilities' as interchangeable verbal formulas and picking whichever sounds stronger, rather than first classifying the proceeding and identifying the burden and standard that attach to the specific issue.
Candidates memorise the two phrases as slogans and never build the habit of asking who bears the burden on this particular fact and what standard applies; they also forget that some issues inside a criminal trial (for example, a voluntariness challenge or an alibi) carry a different burden from the ultimate issue.
What to do instead
Before answering, write three things: the type of proceeding, the party bearing the burden on the disputed fact, and the applicable standard. Drill the exceptions explicitly: the prosecution always bears the ultimate burden, but the defence bears an evidential burden when raising an affirmative defence, and some preliminary facts are decided on a different standard from the merits.
Confusing the burden of producing evidence with the burden of persuading the tribunal, and answering that the party with the persuasive burden must also call evidence first or must rebut every contrary inference.
The two burdens are taught together and candidates collapse them into one idea; they then mis-answer questions about who must go forward when a presumption operates or when the other side has raised a prima facie case.
What to do instead
Keep a two-column mental table: who must produce enough evidence to put an issue in play, and who must ultimately persuade. Practise questions where a presumption shifts only the evidential burden, and where the evidential burden can be discharged by cross-examination rather than by calling a witness.
Answering relevance questions by asking whether the evidence is true or convincing, instead of asking only whether it makes a fact of consequence more or less probable, and then jumping straight to a discretionary exclusion without ever establishing relevance.
Candidates conflate relevance with weight or with reliability; exam items are written so that the evidence is plainly relevant but weak, and a candidate who equates relevance with strength picks the exclusion option.
What to do instead
Use a strict two-step: first state the fact of consequence the evidence is offered to prove and explain the logical link; only then consider exclusion. If the answer explanation says the evidence is 'weak' or 'unreliable', that is a weight point, not a relevance point.
Treating similar-fact or propensity evidence as automatically admissible whenever it is logically relevant, without applying the heightened exclusion test for evidence offered to show the person acted in conformity with a character or disposition.
The relevance analysis is easy and the candidate stops there; the special rule against propensity reasoning is a separate filter that is often tested through a fact pattern where the prior conduct is genuinely probative of something else.
What to do instead
For every prior-acts item, name the non-propensity purpose the proponent claims (identity, intent, absence of mistake, plan, or similar) and then test whether that purpose is genuinely in issue. If the only chain of reasoning runs through 'he did it before, so he did it again', the evidence is excluded.
Evaluating a witness's demeanour and confidence as if they were reliable indicators of truthfulness, and failing to separate the credibility of the witness from the reliability of the identification or the accuracy of the recollection.
Candidates rely on intuition and courtroom-drama stereotypes about shifty or confident witnesses; they also merge the question 'is this witness lying' with 'could this witness be honestly mistaken', which are different inquiries.
What to do instead
Assess credibility through the recognised factors: opportunity to observe, capacity and impairment, consistency with independent evidence, motive, and the presence of corroboration. For identification evidence, treat estimator variables such as lighting, duration, and cross-racial recognition separately from confidence, and remember that confidence does not cure a weak initial observation.
Accepting a witness's account of what another person said as direct evidence of the truth of that statement, without flagging it as hearsay and identifying the purpose for which it is offered.
The candidate focuses on the fact that the witness is in the box and speaking from personal knowledge of the conversation, forgetting that personal knowledge of the utterance is not personal knowledge of the facts asserted in it.
What to do instead
For any out-of-court statement, state the purpose in one sentence. If the purpose depends on the truth of the assertion, it is hearsay and needs an exception; if the purpose is only to show that the words were spoken, their effect on the listener, or the state of mind of the speaker, it is not hearsay for that use.
Citing an exception by name without checking its conditions, particularly treating any prior consistent or inconsistent statement as substantive evidence, or invoking a residual or 'interests of justice' exception as a catch-all.
Candidates memorise exception labels and assume the label is the answer; they skip the threshold requirements such as the declarant being unavailable, the statement being against interest at the time made, or the statement being made before a motive to fabricate arose.
What to do instead
For each exception, recite its elements before applying it. In particular, distinguish prior inconsistent statements used only to impeach from those admissible substantively, and reserve residual exceptions for genuinely exceptional cases with strong indicia of reliability.
Assuming a privilege belongs to the person who happens to be in the witness box, or that a privilege is lost only by explicit waiver, rather than asking who holds the privilege, who may waive it, and whether the communication was made in circumstances preserving confidentiality.
Privilege rules are organised around relationships and holders rather than around the witness, and candidates apply a single generic 'confidential' test across legal advice, medical, and other relational privileges.
What to do instead
For each privilege question, identify the holder, the scope of the protected communication, and the recognised exceptions or implied waiver routes. Note that privilege survives the termination of the relationship and that inadvertent disclosure does not automatically waive it.
Treating improperly obtained evidence as automatically inadmissible, or conversely treating an unlawfully obtained confession as admissible because it is reliable, without applying the separate exclusionary tests for illegally obtained real evidence and for involuntariness.
Candidates merge the exclusionary rule for confessions with the discretion to exclude improperly obtained physical evidence, and they assume a single 'fruit of the poisonous tree' doctrine disposes of every question.
What to do instead
Keep two distinct tracks. For statements, ask first whether the statement was voluntary and, if not, exclude it; then consider derivative evidence. For real evidence, ask whether the impropriety is such that admitting the evidence would bring the administration of justice into disrepute, weighing seriousness, impact on the trial, and the availability of other investigative means.
Ignoring the procedural posture of the question, answering as if every item arises at trial before a jury, and failing to adjust for the different rules that apply at a preliminary inquiry, a voir dire, a sentencing hearing, or an administrative tribunal.
Candidates prepare from trial-focused summaries and never build a mental map of which evidence rules are relaxed or altered in non-jury and pre-trial settings, so they apply the strictest rule to every setting.
What to do instead
At the top of each question, note the forum and stage. Then ask whether the rule in issue is one that applies with full force there; remember that the trier of law decides admissibility on a voir dire and that some hearsay and privilege rules operate differently outside a jury trial.