It's a common misconception that Lex staged this massacre in the desert frame Superman for killing them.
If that's your assumption you immediately question the ridiculousness of that premise because Superman should be easily exonerated by the cause of death… small arms fire and Superman doesn't need guns to kill anyone.
However that's based in two assumptions: First, assuming that Lex was trying to frame Superman for murder; and Two, assuming, exonerating evidence would be readily available.
No one sincerely believes that Superman murdered anyone.
That wasn't Lex's plan and it wasn't the result either.
If they sincerely believed Superman killed an entire terrorist cell, would they invite that person into the seat to government power unchecked? Of course not!
In fact, Lois directly challenges Secretary Swanwick with the idea… if he believes Superman is a murderer he's free to discard the bullet… and we know that instead, Swanwick acts as if Superman is innocent.
Okay, what WAS Lex's plan then?
Lex's goal was to call into question the collateral consequences of Superman's actions for a number of reasons.
- First, simply to screw with and test the Man of Steel;
- Second, to provoke government oversight which he could leverage into access; and
- Third, to cause the public to question Superman.
The public narrative created by the incident is that Superman
unilaterally elected to save Lois. Superman's intervention compromises
the warlord and destabilizes the region when the Nairomi government
comes and retaliates against the weakened warlord; and the villagers
occupied by the warlord become collateral to that conflict.
Superman is accused of performing unilateral state-level interventions
without the consent or the will of the people.
The second assumption, that evidence would be available, whether the fact that the General's men were shot dead or that the bullets were exotic.
Remember, that Lex knows everything and initiated everything at this point.
Anatoli Knyazev is armed, informed, and paid for by Lex.
Lex knows the CIA are there, that's why Knyazev knew to look for and reveal the tracer. Lex is relying on exposing the CIA to provoke the General into taking Lois captive and bringing Superman in.
Lex knew that between the cagey movements of these terrorists, the CIA's involvement, and the Nairomi government, there would be no exonerating evidence coming out of the event.
Note that a tracer implies difficulty in accessing these terrorists. It is so difficult that the CIA had to use Lois Lane's credentials just to get close. So it's hard to get at the evidence in the first place. Then the Nairomi government suppresses evidence because they commit atrocities against the occupied villagers.
Finally, the CIA suppresses and classifies the information because from their perspective, it was their agent getting caught which caused the catastrophe. If there was no CIA, Lois gets her interview and goes home, end of story, no international incident with Superman.
That means evidence didn't matter. Not using suspiciously expensive contractors, not using experimental bullets, not their sudden departure, and not even leaving Lois Lane as a witness!
Nothing exonerating was going to get out to the world at large.
Consider the three pieces of evidence that did get out.
First, you have Lois Lane's account. However, as a Daily Planet reporter with known ties to Superman, she's considered biased… even Swanwick accuses her of inventing a conspiracy to reestablish Superman's halo and her own.
Second, you have the experimental round, explicit tangible evidence, which Central Intelligence suppressed to a degree that even Secretary of Defense wouldn't go on record to disclose.
Third and finally, consider who Congress is listening to. The status quo is that Superman is a beloved public savior with godlike power… if you are going to call that into question during a public hearing, you had better believe you want the best possible evidence before entertaining such a serious accusation against Superman. Yet who do they present? What is their best evidence? It's the testimony of a village refugee who can only give a second-hand account to Superman's actions and a first-hand account about the military response. She wasn't at the compound, she didn't see what happened, she only experienced the tragic aftermath. Insofar as Superman is concerned, she is literally a hearsay witness. If the best the United States Congress can produce is hearsay, then it's clear they didn't get or have access to forensics, ballistics, bodies, photos, or any kind of real evidence.
Lex knew that, planned for that, and that's why it didn't matter how the terrorists died.
Ammunition addendum - Why specialized ammunition?
Whatever specialized utilitarian benefit they were developed for - Greater reliability, longer shelf life, whatever. Pursuant to the above, without fear of trace, why not use optimum equipment?
Conspiracy canary - Lois isn't exactly right in her brief to Perry. It's not that the rounds aren't traceable, it's that they aren't traceable by HER. They're preeminently traceable by Lex. In fact, Lex confronts Lois about that on the helicopter pad, indicating he knows what she's been up to and chasing down- when she counters that she's proven his involvement his retort? "Unfortunately, that will blow away like dust in the desert." He's not above a cover-up and the rounds are a tiny trace bit of evidence he can use to track who is trying to track HIM. Anyone or anything that's coming close via the ammo only ends up on HIS radar FIRST before the person trying to figure out the origin does... because they only people who know are in his pocket. So using the proprietary rounds act like a marked bills or a dye pack. Even if the Nairomi incident is airtight, the rounds allow any snoops to be sniffed out and "blown away like dust."