Motive, Means, and Opportunity

 

Let’s talk about mystery stories. Any story built around a question is a mystery story, so let’s define it a little more. Let’s talk about a mystery story where the question is ‘who did it?’ - yes, let’s talk about a whodunit.

 

A whodunit would be boring if there were only one suspect, so in addition to the victim you also need to present a group of suspects to the reader. During the story, the investigator, no matter whether they’re a professional, semi-professional, or amateur, will then figure out which of the suspects could have done it, narrowing down the list. In order to do that, they will have to see whether the suspect has all three of these: motive, means, and opportunity.

 

The first one on the list, motive, is also the most important one. If the suspect has no reason to want the victim dead, then why would they have done the deed? Even if they have means and opportunity, without a motive they’re not very suspicious. There are three types of motives, to put it down simply.

Money-related motives are the most common. Either the suspect stands to gain something through the victim’s death, such as an inheritance, or they will save money through the victim’s death, such as no longer having to pay support or blackmail money.

Emotion-related motives are quite common in whodunits, too, because it would be boring if it were always about the inheritance. Usually, those motives revolve around hatred and revenge, but there’s also cases where someone kills for a misguided, mutated love of the victim.

Finally, there’s murders committed to keep a secret. Most often, this means committing a murder to hide another crime, such as another murder, a robbery, or a theft. These motives are often connected to the victim being a blackmailer and always to the victim having knowledge of the secret. The secret also can be something like the culprit not really being related to someone, which would get them in trouble if widely known (depending on the era you set the story in).

 

The second one on the list, means, is also the second most important one, because it is a good way to narrow down the list, too. Means usually refer to physical means such as the right tools to commit the murder. If the murder has been committed with a rifle, for instance, only people who have access to a rifle and the ability to use one (skill as well as physical ability) tick off this box and have the means.

Means are a very wide field, of course, given that there’s many ways to kill a person and those ways shift with technical development. In some cases, the means aren’t clear from the beginning or there are not physical means in the way of tools involved. If the victim was strangled, for instance, there’s no tool someone can bring around, but the field is narrowed down to the suspects whose hands are big enough to strangle someone and who do have the necessary strength to do it, too.

In some cases, the means make it unnecessary for someone to be in the vicinity during the actual murder, as with poison put somewhere in advance (“Police at the Funeral” by Margery Allingham does a great job with that, having the murderer kill from ‘beyond the grave’).

 

The last one on the list, opportunity, is also the weakest. There will, most likely, be a lot of people in the vicinity of the victim at the time of the crime. Those who don’t also have the means or the motive are not even real suspects.

Opportunity comes down to alibis and most of us don’t have alibis for the whole day and the whole night. We’re not with other people 27/7 (Siamese Twins excluded), after all, we all need to go to the toilet or take a shower or just have five minutes to ourselves at some point.

Yet, without the opportunity to do the deed, motive and means are meaningless. If the victim’s only heir has the motive (inheritance) and the means (can operate a rifle), but was drinking in a bar two hours away with ten buddies, that heir is no longer really a suspect (unless you wish to give them an accomplice, which complicates matters a lot).

 

Once you’ve figured out these three aspects for every suspect you want to present, you can work the middle of the story very well, because the middle is mostly about the investigator checking the suspects and finding out that they are missing one of the three aspects. They have a motive, but no means. They were in the vicinity, but don’t have a motive. They have means and motive, but were far away at the time of the murder. This is what the middle of a whodunit is about: sieving through the suspects.

The black moment in a whodunit is usually either when the investigator runs out of suspects (someone killed the victim, but who??) or when the investigator finds the culprit, but has no proof to get them arrested.

This is where the twist comes in. Your suspect has motive and means, but no opportunity? Someone at the bar they drank in comes forward and says that they were gone for several hours. Your suspect has motive and opportunity, but no means? You find a device which allows for the frail granny to shoot the rifle successfully. You know that this person did the murder, but you can’t find the weapon they used? You manage to lure them into a trap so they’ll lead you to the hiding place of the weapon (“Columbo” does that a lot and with great success).

 

Motive, means, and opportunity are the three important aspects to figure out for every suspect in your whodunit. Ideally, only one person has all three (unless you want a “Clue” twist where there’s several valid endings), but it will take a long time for the investigator to find that one suspect, because that is what the mystery is about. You want to answer the question at the end, not earlier. You also want to give the audience a chance to guess along, so you need to give them all the information as your investigator gets it - that is very important.

 

Writing a mystery can be fun, but it does need additional plotting to make sure your suspects all have their motive, means, and opportunity down (and are ideally only missing one if they didn’t do it), because the solution usually revolves around those three. Keep that in mind and you can make a great story where the audience can investigate alongside the detective!