Designer’s Notes: GURPS Mysteries

By Lisa Steele

Since the earliest days of GURPS, one of its traditions has been “Designer’s Notes” — a look into the ideas, journeys, and challenges of making our sourcebooks. These notes are often a treasure trove of information, useful peeks behind the curtain even if you aren’t a die-hard GURPS fan. And if reading these notes makes you want to learn more about GURPS, then welcome aboard!

Originally published May 20, 2005

Something is hidden, it must be uncovered. It’s one of the world’s most basic plots, but it is much harder to successfully portray in an interactive RPG setting than you might expect. I wrote GURPS Mysteries, in part, to help GM’s avoid the mistakes I’ve made over the decades in trying to challenge my players with puzzling events in addition to combat. I also wrote it for players trying to figure out what their hardened detective character should do when confronted with a crime scene.

You’d have to live in a cave to avoid exposure to the huge number of mystery books, television shows, and movies currently available. Borrowing ideas from popular fiction is not as easy as it looks. Authors and screenwriters have complete control over their characters. They can present clues in very specific ways to obscure key items in a field of red herrings. They can control who their protagonists talk to, and what questions they ask. More importantly, they control what their characters don’t ask, thus avoiding premature solutions and unnecessary details. GMs in an RPG just don’t have that kind of control over the players or their characters.

“So use reality,” you say, “Mystery fiction is all too contrived anyway.” Most crimes in the real world aren’t really all that puzzling. Most culprits don’t use elaborate alibis and rare poisons; they kill people in mundane ways and are generally easily caught. Real life has loose ends, unreliable evidence, and irrational motives which leave unsettling gray areas in even a solid conviction. The mystery genre and GURPS Mysteries borrow heavily from reality, but twist it a bit in some places (and simplify it a bit in others) to make it more interesting and useful as entertainment.

GURPS Mysteries guides you through the adventure-design process by explaining the genre’s underlying structures: the English-style cozy, the American hard-boiled adventure, and the technologically oriented police procedural. These formats are very good broad structures which can serve as a supporting frame for an adventure. Characters and situations that work in Agatha Christie’s St. Mary’s Meade don’t work on the mean streets of Raymond Chandler’s Los Angeles or CSI’s Las Vegas. Chapter One talks about how to pick the format and structure that works best for an adventure, and how to plant clues and provide useful distractions.You will find discussions of both the classic puzzle-piece plot (define the clues and let the PCs find them in any order) and the ball-of-twine plot (provide clues that lead logically from scene to scene) as ways to structure an adventure.

If you are a player, Chapter One takes you behind the curtain and shows you some of the tricks to plot structure and clue placement. If you don’t want to know how the sleight of hand works, skip ahead to Chapter Two.

Chapter Two is all about forensics, death, and injury, including a discussion of how to get rid of that irksome body and what evidence might be found despite the villain’s best efforts to commit the perfect crime. If you’re a GM who prefers to set up the scene and improvise than plan out your clues and encounters, Chapter Two will help you set the scene well. You’ll also find lots of juicy details about causes of death, ways to identify suspects, and specific crimes including arson, kidnapping, and fraud that make good plot fodder. If you are a player whose character has come upon a crime scene, Chapter Two will give you ideas what to look for and how to interpret what you find.

The third chapter is about interviews and interrogations. Mysteries are about talking to people. (The cozy sub-genre, in fact, is almost entirely about talking, without a single gunshot, car chase, or brawl to stir the blood.) This means taking a detailed look both at how real detectives try to get people to talk, and at the GURPS social interaction rules. This was the hardest chapter to write. Social interaction rules should give a tongue-tied player the same opportunity to play a witty detective that the combat rules give a coach potato to play a martial artist. But, people like to roleplay conversations, interrogations, and accusations in a way that they don’t act out combats. The social rules give players and GMs some ideas how to portray these scenes, and balance skill checks against a player’s acting ability. Chapter Three also suggests some optional rules for using disadvantages as a social weapon. A detective who plays along with a Jealous target’s fears and obsessions for example, will be more successful than a detective who has not recognized this weakness. If you are a player trying to decide what your detective will ask an NPC, this chapter will give you several approaches based on the target and on your character’s skills and strengths.

A GURPS Mysteries adventure can be part of almost any campaign using almost any game system. The ideas used in this book were developed in scenarios for various versions of D&D, Champions, West End’s Star Wars RPG, FASA’s Star Trek, Traveller (several incarnations), and, of course, GURPS. The game system does make a difference in how a mystery adventure works. Chapters Three (social interaction) and Six (paranormal adventures) are useful guides to the common pitfalls in these key areas.

The remaining chapters of GURPS Mysteries discuss time periods and genres: low-tech, the modern era, science-fiction, fantasy, horror, and psionics. You’ll find discussions about specific challenge and opportunities in each genre. There are also various agencies that can be used as employers or adversaries — including thief-takers, the Pinkerton agency, futuristic insurance investigators, and psionic legal investigators. The agencies were created or chosen to show the breadth of historical and modern detective work.

Of course, you will find character templates and advantages/disadvantages/skills. You’ll find examples of the hardworking police detective, the cynical private eye, the genius consulting detective with his deerstalker, and many other possible protagonists. You’ll find crime scene and detection gear too.

There is also, of course, a guide to books, television shows, and movies to inspire GMs and players alike.

Normally in a design article there is a discussion of things left on the cutting-room floor. GURPS Mysteries was fortunate not to have anything major cut for space. As a bonus, however, let me explain some of the art. Chapter 2, Page 38 has a discussion of blood spatters. The editor for this book asked for illustrations of the various patterns. I sent the art department a series of images taken from an in-court demonstration made by Dr. Henry Lee in an actual homicide trial to explain his crime scene analysis. (The original is ink, not blood, but Dr. Lee testified that the red ink has similar properties.) The blood stains illustrating the book correspond with some of the topics on this page.

Low-velocity patterns are found on pages 59 and 99. These could be caused by blood dripping from a wound onto a floor or other level surface. The size of the drop increases the farther the drop of blood falls onto the surface. The images on pages 36, 48, 75, 81, 89, and 90 are also low-velocity patterns, but here the surface is inclined — the sharper the incline the longer the drip. The mathematically inclined could use trigonometry to figure out the exact angles; when a sphere of blood strikes a flat surface, the diameter of the sphere in flight equals the width of the stain and the length of the stain is equal to the hypotenuse of an inverted right triangle. The effect on inclined surfaces is similar, but you would need to separate the original impact from the elongated drip due to gravity. In an adventure or a real crime scene if the shape and drip do not match the orientation of the object, it may be a clue that the object had been moved after the crime.


Medium-velocity patterns are found on pages 3, 29, 77, and 96. This is the kind of pattern produced by blood flung off a weapon by centrifugal force as it is swung (“cast-off”) or from an arterial wound. You can also see a contact hand-print next to the medium-velocity pattern on page 3 and 29. It is enlarged on pages 77 and 96. This could be caused by the attacker or victim touching the surface for support after the assault or homicide.


A high-velocity pattern is on page 7 at the bottom. This is the kind of pattern you would find from a gunshot, explosives, or possibly coughing or sneezing. The medium and high velocity patterns appear to come from a single point. With larger patterns, criminologists can draw lines through the center of individual stains to find the point of convergence where the blow was struck.


Contact wipes are on pages 24, 53, and 112. (Here, someone has touched blood and wiped it across a surface.) The swipes on pages 8, 44, 54, 62, 120, and 121 are all contact smears; the person has blood on their hands or clothing and has smeared it onto a surface — longer swipes mean faster speeds.

Sadly, every project must come to an end. I would like to thank Jonathan Turner, who lent me his prodigious library of mystery novels and helped write and re-write the first chapter and Allen Wilkins, my husband, for editing the various drafts. Between the change from GURPS Third Edition to GURPS Fourth Edition and from a printed book to e23, this project was three years in the making. I’d also like to that the editors for patience with questions and with a series of word-processor incompatibility woes.

Even with the delays, I did not get a few last sources into the manuscript. Here are some books that I came upon after the book was written which I commend to the GURPS Mysteries purchaser.

On Forensics

  • Baden, Michael, Dead Reckoning: The New Science of Catching Killers, (Simon & Schuster 2001) (New York City Medical Examiner’s discussion of forensics and famous cases).
  • Horswell, John, The Practice of Crime Scene Investigation, CRC Press (2004) (another practitioner-oriented text on crime scene work with useful pictures and diagrams).
  • Lyle, D.P., Forensics for Dummies, Wiley Publishing, Inc. (2004) (a great resource for GMs and players surveying forensic methods: the last section on Hollywood myths is useful for RPG GMs looking for more verisimilitude in their adventures).
  • Doyle, James, True Witness: Cops, Courts, Science, and the Battle Against Misidentification, Palgrave (2005) (history of the struggle between research psychologists and lawyers over how eyewitness testimony is used in criminal trials).

On Policing and Crime outside the U.S.:

  • Etienne, Steven, Maynard, Martin, and Thompson, Tony, The Infiltrators, Penguin Books (2000) (undercover work in Scotland Yard).
  • Gray, Roger, The Trojan Files, Virgin (2000) (armed policing in and around London).
  • Hames, Michael, The Dirty Squad, Warner Books (2000) (policing obscenity).
  • Latham, Richard, Deadly Beat: Inside the Royal Ulster Constabulary, Mainstream Publishing (2001) (an RUC officer’s-eye view of the force).
  • Ryder, Chris, The RUC: A Force Under Fire, Arrow (2000) (a historical view of the force).
  • Townley, Lynne, Ede, Roger, Forensic Practice in Criminal Cases, The Law Society (2004) (guide to UK forensic practice written for lawyers).
For fans missing some of their beloved supplements that have been out of print for years, you have reason to smile! We’ve recently started making many classic books available thanks to print-on-demand magic; for a full catalog of those offerings, see our On Demand page. We recently added GURPS Mysteries and GURPS Spaceships!
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