Murder Mystery Card Game rules

Just a placeholder for this card game I'm thinking up. It's a party game similar to Mafia or Are You A Werewolf. This entry will be edited as the game takes shape.

I know you can't copyright game mechanics, but like most people, I can't help but put my creations out on the internet vainly for everyone to see. Let's just hope I try to make the game and don't do nothing again, like every time I have a great idea. Lazy me.

BARE BONES BASIC RULES

• For 6 or more players.
• A facilitator is desired; at a bare minimum, someone has to set up the deck and deal them out.
• The facilitator starts the game by taking out the murderer card from the deck and shuffling the rest. Then he or she counts out enough cards for the party, minus one, then adds the murderer card. The resulting stack should have enough cards for one card for each player. The cards are shuffled and dealt, face down. The cards must remain completely secret from everyone else until the end of the game!
• The facilitator announces the setup. ("There has been a murder tonight! The murderer is someone in this room!")
• Each card has a profession (or is the murderer) and some yes/no combination of capability, motive, and opportunity (C/M/O) - almost always 2 out of 3, but the murderer has 3 out of 3 C/M/O.
• The last player who has lost a pet goes first.
• During a player's turn, the player gets to ask two kinds of questions.
• One yes/no question about C/M/O to a second player of their choosing. ("Did you have the opportunity to commit this murder?") The second player must tell the truth about what is printed on their card, whether the answer is yes or no.
• The first player may ask any number of other questions of any sort to any and all players during the turn, including "Are you the murderer?" or what their profession is. The questioned player may lie about any question not related to C/M/O. These additional questions can be asked before or after (or both) the one C/M/O question. The turn is over when the first player has no further questions.

• Play continues clockwise. The next player can ask questions of a different or the same person, as they choose.
• After 3 of the players take a turn, everyone votes on who is the murderer. This person goes to "jail". If it is the murderer, game is over, everyone but the murderer wins. If not, play continues. The player in jail loses his or her turn for the rest of the game (if they haven't taken it already), but they can vote.
• Play continues with another 3 people taking their turns. After another three people take their turn, voting occurs again.
• Each person only gets one turn in the game, unless they are jailed before they can take it. When the last person's turn is used up, the party has one last vote to try and jail the murderer. (The game cannot end on two votes in a row!)
• If the murderer is still not caught, the game is over and the murderer wins.

DELUXE RULES

• At the beginning of the game, the facilitator uses his or her boundless imagination to create a scenario. Then, he or she explains who was murdered, and how, where and with what the victim was murdered. Each time a player is asked a C/M/O question, they must explain why the answer is no, or why they are not the murderer if the answer is yes, in the vein of the profession on the card. ("As a famous actor, I simply would not have had the opportunity to slip away and murder the victim!")
• Alibis: at any time during the game, two or more people can proclaim they are each other's alibi. This means that both players are exempt from being voted on. People who have already said no to a C/M/O question (and are automatically not the murderer), cannot have alibis. Either player in an alibi can choose to cancel it at any time. If someone holds an alibi with the murderer at the end of the game, that person is a double loser! (Optional Rule: the next game a double loser plays, the loser has to take the "Drunkard/Fool" card face up before the cards are even dealt!)

PROFESSIONS
Come a landsman, a tinsman, a tinker or a tailor
a doctor, a lawyer, a soldier or a sailor
a rich man, a poor man, a fool or a witty
Don't let her die an old maid, but take her out of pity.
(Possible name: Take Her Out Of Pity, from the song)


Any list of professions must have three variations (so as not to memorize the C/M/O list of any one profession). This also prevents the murderer from being easily found due to pretending to be a unique profession that another player already has.

Of course, if you just throw out professions willy nilly, the deck would get huge, and the types of professions would be harder to memorize. I already know there's going to be a profession list on one of the cards for reference.


SPECIAL CARDS

• Special cards are professions that can be added to the deck. It is suggested that they be added in this listed order.
• Patsy: Has all three C/M/O, but is not the murderer. (Suggested for 6+ players)
• Politician: Can take his turn, even if jailed. (Suggested for 9+ players)
• Drunkard/Fool(?): Has none of the C/M/O. (Suggested for 12 + players)

What do these rules imply? 

It's different from Mafia. It's not all social deduction, until it is.You might think there's some easy deduction going on. Anyone who answers no to a C/M/O question is automatically not the murderer. Easy, except...you cannot win the game through logical deduction alone unless you are very lucky. The game lures you in with a simple logic puzzle, then hits you with a decision to made on incomplete information. It might take a pen and paper to keep track. Perhaps the facilitator could keep track.


Since most professions have 2 out of 3 C/M/O's most of the time, It is thought that any group, after all the turns have gone, have eliminated ~1/3 of the players as suspects. This, of course, may vary through luck, but it's obvious that there has to be guesswork involved. This is where the "social deduction" comes in. Adding in the ability to ask people unrelated questions (including, "Are you the murderer?") adds in the opportunity to watch people faces; how do they lie? Are they hiding something?

Players should familiarize themselves with the professions on the cards, for if they become the murderer, they will have to pretend to be another profession (which a sharp sleuth would catch if it was made up).

UNDERLYING MATH

The underlying math dictates the gameplay, much like Mafia. It is shown that the Mafia normally keeps ~50% chance of winning any game, but in reality is likely to win due to "social deduction" hence the name of the genre. Due to the fact there is never more than one killer, the mechanics to keep the chances of success balanced in my game are modified. Given that each player has a 1/3 chance of being ruled out (if someone asks them a C/M/O question they can respond 'no' to), the choices for murderer are 2/3 of the people. (Of course, luck might provide more or less help depending on who gets to answer 'no'.) There is a vote that removes a second person, but how often should that happen? By designating it as every three turns, it narrows the suspect list down to ~1/3 of the players. This keeps the possible suspects at roughly 1/3 no matter how many people are playing. This makes the average number of final suspects very small: 2 in a six player game, 3 in a nine player game, and so on. This is why it is suggested that, of the special cards, the Patsy is added first. It artificially adds an additional suspect to give the murderer a better chance of not being chosen. Then, as the number of players rises, the card additions give greater and greater advantages to the innocents to counter the number of final suspects as it goes up.

The number of players dictates the chances of the murderer getting caught in several different ways. First, the greater the number of players, the harder it is to find the murderer (though as I explained above, there are mechanics that help). Also, if there is a number of players not divisible by 3, the players get an extra round of voting. Therefore, a group of players whose number is 3x+1 has the best chance of finding the murderer, as it gives you an extra vote for the fewest number of additional players.

The smaller the number of players, the more luck is involved in finding the murderer. The chances of eliminating greater than 1/3 of the players as suspects is high if there are only 6 players, as compared to 18, due to a lack of precision.