Although a plaintiff in a S1983 suit needs to be able to identify the law enforcement officer who injured him in order to present an issue for trial, an allegation of after-the-fact conspiracy supported by omissions or inconsistencies in contemporaneous records can present an issue for trial on the same facts.
http://www2.ca3.uscourts.gov/opinarch/172594p.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.