Re-using a public key seems like an incredibly basic mistake. How is the chain of custody for digital evidence handled by intelligence agencies and 3rd party r

Re-using a public key seems like an incredibly basic mistake. How is the chain of custody for digital evidence handled by intelligence agencies and 3rd party researchers? Are there higher standards with regard to digital evidence? It seems to me that with digital evidence, ultimately you at least have to trust the investigatory agency at hand. But we're past that, because a huge number of Americans like myself will never trust any information from the US government.