During a visit to the planet Galar, the team is introduced to a technology that allows memories to be implanted into a person's mind; Mitchell hits it off with Reya Varrick, one of the scientists working on the device, only to be accused of her murder when she ends up dead after they spend the night together. He claims to remember killing her, and the team must find a way to prove that the memory has been implanted and is not really his.
"Collateral Damage" provides examples of the following tropes:
- An Arm and a Leg: It's revealed through one of Mitchell's childhood memories that his father was a test pilot who had both legs amputated following a bad crash.
- Compliment Backfire:Varrick: You know how it is with scientists. We spend so much time in the lab, I think that's where we feel most comfortable.Mitchell: In your case I find that hard to believe.Varrick: Are you suggesting I don't work as hard as my colleagues?Mitchell: No! No, God, no... That was supposed to be a compliment.Varrick: Guess I'll have to take your word for it.
- Death by Sex: Varrick is killed after taking Mitchell home, though it's not clear if they actually have sex or not; all we see is them kissing in the kitchen.
- Frame-Up: Varrick's ex-husband Morrell frames Mitchell for the murder by erasing his own memories of the event and implanting them in Mitchell's mind, assuming that he would claim diplomatic immunity and the whole thing would be swept under the rug.
- Hired to Hunt Yourself: After erasing his memory of the murder, Morrell is distraught by the death of his ex-wife and works harder than anyone to bring the culprit to justice. He winds up revealing himself as the true killer after helping Mitchell identify an abnormality in the implanted memory.
- If I Can't Have You...: Mitchell deduces that Morrell never got over Varrick after their separation and killed her out of jealousy after seeing her leave the party with Mitchell.
- Is That What They're Calling It Now?: After Mitchell spends most of the party flirting with Varrick:Mitchell: I don't think diplomacy is my thing.Daniel: Oh, that's what you're doing.Mitchell: What?Daniel: Nothing, nothing.
- In Medias Res: The opening of the episode shows Mitchell waking up and being arrested the morning after the murder, before going back twenty-four hours earlier to show How We Got Here.
- Karma Houdini: After Morrell is outed as the real killer, the Emissary has his memories re-erased and allows him to continue working on the memory project believing that Varrick died in an accident, since he's now the most qualified scientist available.
- Married to the Job: Varrick claims that her marriage fell apart as a result of her obsession with her work.
- My Greatest Failure: It's revealed that Mitchell accidentally bombed a convoy full of refugees due to faulty intel back when he was a captain, something he's never been able to forgive himself for.
- Narrative Profanity Filter: Landry's comments on the team's mission reports at the end of the episode:Landry: Not sure I've ever seen language like that used in an official Air Force document before.Mitchell: Sorry about that, sir.Landry: Oh, you should have seen what Colonel Carter and Dr. Jackson wrote.
- Red Herring: To draw suspicion away from Morrell, it's implied throughout the episode that the Emissary had Varrick killed due to their disagreements over the military having control of the project. However, this is subverted somewhat once the truth comes out, and the government decides to wipe Morrell's memory (and make him believe Reya died in an accident) rather than let the truth come out "for the good of the project" (due to him being the most qualified person to run it after his ex-wife).
- Shifting the Burden of Proof: Discussed:Emissary: This is hardly proof of Colonel Mitchell's innocence.Daniel: Wow, on Earth you have to prove guilt.
- Techno Babble: Walter attempts to relay some medical jargon from Dr. Lam, with predictable results.Walter: She wanted you to know that the troponins were negative, but the CK and the myoglobins were up... No, wait. Um, the myoglobins were negative but the CK and the troponins were up. No, wait—Landry: Walter.Walter: Sir, whatever it was, it means that when the sample was taken Colonel Mitchell had been recently either stunned or rendered unconscious by some kind of electrical charge.
- Transferable Memory: The memory device is developed from Goa'uld technology to allow the transfer of memory from one person to another. The Galarans seem to want to use it primarily for teaching purposes, and Landry mentions that the Air Force is keen to get its hands on it for similar reasons, but Daniel is wary about the ethical implications from the get-go and a lot of the shine wears off for the rest of the team after it's used to frame Mitchell for murder.
- Wham Shot: Mitchell seeing Morrell in place of his own reflection in the mirror while looking for inconsistencies in his memory of the murder.