Researching a novel - q about a single key witness to murder?

Perp is pulled over and taken into custody for traffic violation / DUI. He is fingerprinted and his prints are run through AFIS (Automated Fingerprint ID System). His prints match those from the 7-year-old the murder scene / on murder weapon…

The murder weapon could have been disposed of in a number of places where it could remain hidden for years and suddenly turn up—buried underground, in the wall of a building, in a body of water, etc.

To remember a detail seven years after the murder, it has to be a pretty vivid detail. Also, it has to be something that wouldn’t already have been detected by the investigators. It probably also has to be visual, creating a strong image in the witness’s mind. It could be something as small as a distinctive monogrammed handkerchief used to hold the knife/gun…or it could be the killer’s seven year change from female to male.

Have you considered a witness that is an unlikely one, perhaps an idiot savant i.e. Dustin Hoffman in Rain Man? Perhaps she is no longer in an institution (was on a day trip from said institution and saw the murder by chance) but now lives on the streets as a homeless person?

This might make the novel a bit more complex, i.e. two timelines that don’t have much in common until the close of the story, but would give it that neat twist you might be looking for.

I’m thinking that this evidence might be found in the form of a photograph that the eyewitness took 7 years earlier. The photo could be a picture of the murderer driving a rental car that contained blood from the victim. No link was ever made between the murderer and the rental car but the photograph is indisputable proof of them driving that car.

The witness had framed the picture and had always wondered about the man in the car, even though it wasn’t the focus of the picture. Something about the expression on his face stood out and when she saw the same man on the news being brought into the courthouse, she showed the photo to the police.

You could go with a child witness that comes forward as an adult. They remembered a turn of phrase from the murderer and didn’t think much about it at the time. Or they were afraid of the murderer because it was someone they knew or in the family.

I also like the idea of finding something in a recently deceased relative’s or close friend’s things -maybe something like the photo @fireside mentioned.

You could go with someone not from the area that saw something on one of those cold case shows that reminded them of something they saw on a trip years ago.

Or maybe two people who had a falling out years ago and recently had cause to get back in touch with each other (e.g. brothers after the death of a father) are talking and realize they have different bits of information that fit together. Maybe someone told two different lies to them.

@riskyBusiness Welcome to Fluther
Now I am gonna steal your idea.

How about the woman accuses the man of rape, they take his dna sample, find it doesn’t match the rape, but does match the murder 7 years ago.

I agree with what fireside suggested.

Something tangible would be best 7 years later. Also, physical evidence is necessary for conviction, so it’d be helpful if the murderer had a piece of physical evidence linking them to the crime (after all those years).

I’ve heard that many criminals cannot resist taking a “souvenir” from their victims…perhaps the killer couldn’t resist taking something that they figured no one else would notice was missing from the victim. (simple necklace, a spoon, a sock…need not be expensive, but does need to be something the original investigators would overlook).

Just plant an unmistakable flaw or habit for the murderer, then have that come up in the evidence somehow…

In other words jsut foreshadow basically anything you want and it will be ok ;)

Go read “The Girl with the Dragon Tattoo”. It uses a very similar plot/discovery device to the one mentioned by @fireside above. Also, it is a very good read and would be great inspiration for you in your current writing endeavor.

(I am not going to mention the exact nature of the device here, as it would spoil much of the plot of the novel)

On the night of the murder, the murderer has plausible alibi that he was out of town/state/country but, in fact have him/her be in the immediate area of the killing and of a traffic accident. While fleeing the scene of the crime, one of the drivers sees him/her and needing a witness, writes down the the license plate number of the car the killer was driving.

If someone gives you an idea that you use, I hope you will credit this person in your novel’s forward :)

Several years later the 15 year old is 22. Ahhhh, she remembers, flashes of images not understood, until…............she tells her psychologist, she has been seeing for 2 years, and he reveals her secret. A witness to the witness!