Prosecutors allege that Jefferson demanded kickbacks in return for using his influence as a congressman to broker business deals in Africa. Although the frozen cash links to just a small part of the 16-count indictment — the allegation that Jefferson planned to bribe the Nigerian vice president — it is by far the government’s most sensational piece of evidence.

Keeping $90,000 in a freezer requires “a fairly decent explanation,” said Thomas Green, a Washington partner at Sidley Austin.