So I was writing a scene where some charters space a dude and then edit the camera footage to make it look like a suicide. That’s when I realized I had an issue. With good editing software and a “faulty” airlock monitoring system I can make any murder look like an accident or vise versa. For example make a video of them leaving a death note and then have them go out in the airlock and die OR have them go out in a EVA suit and have their decompression alarm go off and the airlock rescue system fail. Since space travel is very dangerous and systems would regularly have glitches and malfunctions due to their complexity. So the question is how can I stop every deranged killer form spacing whoever they want?
Same way we stop serial killers on Earth
There are 4 main ways we do it:
- Someone gets away. Many serial killers are caught by the "one that got away". They mess their attack / leave for dead someone who survives / free someone out of pity / leave the dungeon unlocked and let them get away / etc. The escapee makes a statement to police with new details, and that breaks the case for the cops.
- In your case, they try to get someone into the airlock and they fight back. Maybe they have a weapon on them when attacked. Maybe they know the airlock systems and can stop the sequence quickly using a hidden workaround.
- They get sloppy or brazen. Serial killers typically mess up their first murder or two, then are meticulous and flawless for a time, and then let their guard down and make mistakes.
- In your case the first one the camera footage editing might be flawwed but the detectives miss it cause it looks like suicide. Then next 10 are flawless. Number 12 they cut the footage too close and a reflection gives it away.
- Everybody is on guard. Nobody walks alone at night. Everyone carries panic alarms and their family share gps tracking apps. The killer gets desperate to kill so changes their pattern and mucks up.
- After 20 "suicides" from a crew of 100 nobody is going to buy the suicide narrative. Some detective puts their own hidden cameras by all the airlocks to catch the next one. Or, someone concerned that they're going to be suicided next just welds the doors shut. So the serial killer uses a knife next time, or uses a more visible airlock, or spends longer there breaking the welds. All changing his pattern and increasing his chance of detection.
- Statistics and probability. There have been serial killers caught because police used statistics to profile their commute to killing from home and got a heat map of their likely residence. A theif at my work was caught by simply matching theft dates to employment rosters. Nurses killing patients have been detected by similar means.
- After a pattern of suicides he may find himself under extra surveillance simply because of elimination. (Hey there's been 7, and all 7 occurred on a night when Dave is working in the security suite and logged into the camera suite - that's a coincidence. Maybe we should watch him.)
- This is how security caught a nightfill manager at my old store who was stealing. He turned the lights off, then the cameras off. Then loaded up his car with stock, then turned the cameras back on again. When looking at the tape he just went home for the night, and the blackness hid the glitch. Additional cameras were installed on a hidden system after months of investigation - and they caught him. It was only because maths showed we didn't have enough customers to fit that stock in their pockets so logically it had to be someone else.
A code embedded into all video images that uses the exact physical properties of the camera to determine which camera it is and if the images might be altered. This also functions as a time-stamp.
While theoretically any digital data can eventually be reproduced and altered doing so correctly can be made hard. For example through the storage medium.
Alternatively you can dress people in vivid colors and let social manipulation and limited time discussions determine who is the killer among them.
Security footage or official logs of the ship should simply not be accessible to random crew members. There is absolutely no point in having security footage at all if it's simple enough for anyone to edit the tape in an undetectable manner. Keep security footage/logs in a secure location - problem solved. This seems a little like asking why bank robbers don't just delete the security footage of their crime before escaping - a system should never be designed so that that is even possible.
Similarly, something as important and dangerous as the airlock control isn't simply a switch on the wall. Any use of the airlock requires the use of a password or PIN or other identifier. Any use of the system will be logged with exactly who took the action.
tl;dr You can't
Just as it's really quite hard to stop people disappearing overboard on private yachts, especially if nobody knew they were on board in the first place.
Passenger and crew manifests are your key. This of course only applies when there are passenger and crew manifests. Hitchhikers aren't on the list especially when the Dentrassis let them on, murdering hitchhikers is a fine American tradition.
You can use the manifests to see a pattern of disappearances that coincide with another person being on board, but that's about all you can do. This only applies to serial killers of the random target kind, not the known person kind. It also assumes you have only one using the same modus operandi, if you have several then you're stuck.
In practice, this is something highly likely to happen once space travel reaches the level of being freely available to all, and entirely a reasonable thing for a Scifi writer to address, but just as many real Earthbound hitchhiker serial killers were never identified, the same will apply in space travel.
Sorry if I'm borrowing from science fiction games like Dead Space and Star Wars Knights of the Old Republic 2. I believe there were situations like that in both games. It's great for narrative imo - dead bodies floating around and they can't speak, but their audio logs can!
I know the Bioshock games were very heavy on audio logs and finding bodies of the people you have a log for, when someone murdered someone else you can find logs of it. It's a trope at this point.
Someone was just spaced on The Expanse, and it seemed like the character had their audio log running and transmitting but it seems like no one got the message. I could be wrong - I'm not caught up - but that would be one way for you to catch a bad guy in the act - with cool space suit audio log gear!
There are more than cameras.
What are we, looking for Bigfoot? Well, OK. But on a spaceship there is not going to be a motion triggered trailcam and that is it. Besides visual data there will be heat sensors. There will be vibration sensors. Electrostatic integrity of the hull will be monitored for punctures. Air pressure and composition will be monitored. There will be sensors for hard radiation and cosmic rays penetrating the hull. My Honda does most of that stuff and it is 11 years old! None of these things are for monitoring the movements of the crew but any of them can be used for that. The presence or absence of crew affects all of these recordings.
Also, is this recorded data going to be stored on a videotape in the managers office? Well, that is ok too. But if I am the ship's owner I am going to want to know what is up and that will be hard to determine if the tape, manager and ship is a cloud of hot plasma. These ships stream their data in realtime. It might take a while for that data to get to me but light is hard to catch.