Investigation Methods

1. The Motive / Means / Opportunity Grid

In short: a simple table that forces you to check three separate things about every suspect, rather than jumping to a conclusion based on just one of them.

Why it matters: the biggest trap in any investigation is deciding someone's guilty because they seem guilty — usually because one thing about them stands out — and then only looking for evidence that supports that feeling. A good investigator checks all three questions for everyone, not just whoever feels most suspicious right now.

The three questions

• Motive — Why might this person have done it? What did they have to gain, or to lose?
• Means — Could they physically have done it? Did they have the ability, the access, the specific method available to them?
• Opportunity — Were they actually in a position to do it? Where were they, and can anyone confirm it?

Why all three matter, not just one: someone can have a screaming, obvious motive and still be innocent, if they had no opportunity. Someone can have had the perfect opportunity and no means at all. A strong case needs all three to genuinely line up — and a big part of your job tonight is noticing when they don't.

How to build one: one row per suspect, one column for each question. Keep entries short — a phrase, not a paragraph. Update it every stage, as new evidence changes what you know. An empty box isn't nothing — it's a prompt to keep looking, not proof there's nothing there.

2. Building a Crime Timeline

In short: a single, growing record of exactly when everything happened, and how confident you are in each entry.

Why it matters: most real breakthroughs come from noticing that two things can't both be true at once — someone claims to have left at 7pm, but something places them there at half past. That's only visible if the timeline is accurate and complete enough to compare against.

The key distinction — the one thing that trips people up: always separate what's confirmed (a receipt, a camera, a phone record — something independent of anyone's word) from what's claimed (someone's own account of where they were). These are not the same category of fact, and treating them the same is the most common mistake in this kind of work.

Methodology

1. Start with everything confirmed by hard evidence. Plot these first — they're your fixed points.
2. Add each person's own claimed movements, clearly marked as claims, not facts.
3. Look for gaps — stretches of time nobody can account for, for anyone.
4. Look for overlaps or contradictions — does anyone's claim conflict with a confirmed fact, or with somebody else's claim?
5. Revise constantly. A timeline built in an early stage will need correcting as later evidence arrives — that's normal, not a failure of the earlier version.

3. Building a Psychological Profile

In short: an honest read of a person's character, credibility, and state of mind — based on how they present themselves, not just what they say happened.

Why it matters: two people can give you the exact same information and mean very different things by it. One might be an anxious, honest witness who's simply bad under pressure. Another might be a calm, practiced liar. Telling those apart matters as much as the facts themselves.

What to actually look at

• How they tell it, not just what they tell you. Defensive? Evasive? Suspiciously smooth and rehearsed? Genuinely upset, or performing being upset?
• What they volunteer versus what only comes out under pressure. Information freely offered reads very differently from information only admitted once someone's confronted with proof.
• Consistency across multiple tellings. Does their account shift in small ways each time they repeat it? Small, natural variation is normal. A story that's suspiciously identical every single time, word for word, can be its own kind of red flag — so can one that changes on the details that matter.
• Their relationship to the victim and to other suspects. Motive isn't just about money — jealousy, resentment, loyalty, and fear all shape how someone behaves and what they're willing to say.

An important separation: credibility is not the same as likability. A charming, sympathetic person can still be lying. An abrasive, unlikeable one can still be telling the truth. Try to judge the account, not how much you warmed to the person giving it.

4. Contradiction Spotting

In short: actively comparing every account against every other account, and against the physical evidence, looking for places where two things can't both be true.

Why it matters: contradictions are often the first hard crack in an otherwise convincing story. They don't prove guilt on their own — people misremember innocent details all the time — but they tell you exactly where to press.

Three places to look

1. Between two people's accounts of the same event. Do their versions actually match, or just sound similar?
2. Between someone's account and the physical evidence. Does their timeline hold up against a receipt, a camera, a phone record?
3. Within one person's own account, across multiple tellings. Did their own story change?

Not every contradiction means the same thing. Learn to sort them:

• Minor and explainable — small differences in timing, memory of who said exactly what. Normal, especially under stress.
• Significant and unexplained — a flat factual conflict with hard evidence, or a detail that changes in a way that conveniently helps the person telling it.

Methodology: when you find one, don't just note it and move on — ask what it would take to explain it innocently. If you can't find a reasonable innocent explanation, that's a contradiction worth pursuing properly, not just filing away.

5. Preparing a Case Summary

In short: pulling everything you've built — timeline, grid, profiles, contradictions — into one clear, evidence-based account of what you believe happened and why.

Why it matters: a good theory that nobody can actually explain clearly is barely better than no theory at all. By the end of tonight, you'll need to present your conclusion in a way that would genuinely hold up if someone pushed back on it.

Structure that works

1. State your conclusion first. Who, in one sentence. Don't make people wait for the reveal — that's a script, not an investigation.
2. Walk the evidence chain, in order. What's the first solid thing that pointed you there? What confirmed it? Build it the way you actually discovered it, not necessarily the order it happened in.
3. Address the strongest alternative theory directly. If there's a good reason someone might think it was somebody else, say so — and explain specifically why your evidence outweighs it. A summary that ignores the obvious counter-argument is weaker, not stronger.
4. Anchor every claim to something specific. Not "he seemed guilty" — which exhibit, which statement, which timestamp. If you can't point to where a claim comes from, it's not ready to go in the summary yet.

6. Evidence Weighing

In short: sorting evidence into tiers based on how reliable it actually is, and being honest about what each tier can and can't prove on its own.

Why it matters: not all evidence is equal, even when it all feels equally compelling in the moment. A rumour and a fingerprint match are not the same kind of fact, and treating them the same — or dismissing the weaker one entirely just because it's weaker — both lead to bad conclusions.

The four tiers, strongest to weakest

1. Hard forensic or physical fact — DNA, fingerprints, timestamped records, camera footage. Exists independent of what anyone says.
2. Corroborated testimony — two or more independent people, who haven't coordinated, saying the same thing.
3. Uncorroborated testimony — one person's account, with nothing else backing it up yet.
4. Hearsay — someone reporting what somebody else supposedly said or did. Secondhand, at best.

Methodology:

1. Sort every piece of evidence into one of the four tiers as you encounter it.
2. Ask what each tier can actually support on its own. Hard fact can carry a conclusion by itself. Corroborated testimony is strong, but still worth checking for coordination between the witnesses. Uncorroborated testimony needs something else behind it before it can settle anything. Hearsay should never be the sole basis for a conclusion — treat it as a lead worth chasing, not an answer.
3. When two pieces of evidence conflict, the higher tier generally wins — but don't throw the lower-tier evidence away. It can still explain a gap, or point you toward what to check next.

7. Gap Analysis

In short: deliberately asking what's still unexplained, checked against every suspect — including your current favourite — not just the ones you're not sure about.

Why it matters: the moment a room settles on a leading suspect, there's a natural pull to stop looking for anything that complicates that theory, and only keep gathering evidence that confirms it. Gap analysis is the direct countermeasure — it forces you to keep checking your own leading theory as critically as you'd check anyone else's.

Methodology

1. For your current leading suspect, ask: even if they did it, what still doesn't add up? Unexplained access, unaccounted time, a detail that doesn't quite fit?
2. Do the same for every other suspect, regardless of how unlikely they currently feel.
3. Revisit this list every stage. Some gaps will close as new evidence arrives — but check for new ones opening up too, not just the old ones closing.
4. Be honest about gaps that inconveniently don't fit your favourite theory. Don't quietly drop a loose end just because your current answer is otherwise satisfying.