Expert Evidence and NumbersThe prosecutor's fallacy: a match probability is not a guilt probability.Criminal JusticeThe chance of seeing this evidence if the person isinnocent is not the chance they are innocent giventhe evidence.P(evidence | innocent) ≠ P(innocent | evidence)Match odds 1 in a millionNot the odds of guiltDepends on the poolLarge database searchedChance matches riseAllow for search sizeTwo rare findingsDo not simply multiplyIndependence must holdTHE COMMON MISTAKEOne in a million match, so guiltyAsk how many people could matchTransposing the conditional is the prosecutor's fallacy, and it has contributed todocumented miscarriages of justice.Educational reference. Courts increasingly expect likelihood ratios withstated assumptions rather than bare probability claims.Expert Evidence and Numberslearnposters.com
Expert Evidence and Numbers — printable law & society wall chart from LearnPosters. Free vector PDF, US Letter and A4.

What’s on the Expert Evidence and Numbers poster

The rule, 3 worked examples, and the mistake everyone makes.

Educational reference. Courts increasingly expect likelihood ratios with stated assumptions rather than bare probability claims.

Questions about the Expert Evidence and Numbers poster

What’s on the Expert Evidence and Numbers poster?
The rule, 3 worked examples, and the mistake everyone makes. The chance of seeing this evidence if the person is innocent is not the chance they a…; P(evidence | innocent) ≠ P(innocent | evidence); Match odds 1 in a million = Not the odds of guilt; Large database searched = Chance matches rise; Two rare findings = Do not simply multiply; Common mistake: One in a million match, so guilty → Ask how many people could match. Educational reference. Courts increasingly expect likelihood ratios with stated assumptions rather than bare probability claims.
Who is the Expert Evidence and Numbers poster for?
Expert Evidence and Numbers belongs to the Criminal Justice section rather than to a school year, because law & society is not something one grade owns. Anyone learning forensic science can pin it up — a beginner, a student mid-course, or someone revising years later.
When should you use the Expert Evidence and Numbers poster?
Use it whenever a forensic statistic is restated as odds that a defendant is guilty. A wall chart earns its place by being glanceable from where the work is happening, so Expert Evidence and Numbers belongs on the wall where that law & society work actually happens, within glancing distance, rather than filed away.
What other posters go with Expert Evidence and Numbers?
Chain of Custody, Crime Scene Management and Digital Evidence sit alongside Expert Evidence and Numbers in the Criminal Justice section. Printed together they make a wall rather than a single sheet, which is how a reference set actually gets used.Chain of CustodyCrime Scene ManagementDigital Evidence
Is the Expert Evidence and Numbers poster free to download and print?
Yes. Expert Evidence and Numbers downloads as a free PDF with no account, no email and no watermark, like everything else in the Criminal Justice section. Print as many copies as you like for a home, a classroom, a library or a tutoring group; reselling the file is the only thing the licence rules out.Read the licence
What size does the Expert Evidence and Numbers poster print at?
Expert Evidence and Numbers is a vector PDF laid out for US Letter, and prints on A4 with Fit to page — the same file, no separate download. Because every mark on it is drawn rather than photographed, it stays sharp enlarged to A3, A2 or A1 at a copy shop. Colour carries emphasis only, so a greyscale print of Expert Evidence and Numbers loses nothing.Printing guide

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