First, get good facts.
Second, remind the judge that "[w]hen faced with
a close criminal case, the judge’s experience with parallel issues in civil
cases may prove helpful in deciding the
boundaries of permissible inferences when the government must prove its case
beyond a reasonable doubt—which is so much more stringent than the civil
standard of proof."
That's what the Seventh Circuit recommended judges deciding close Rule 29 motions think about last week in United States v. Garcia. There the Circuit reversed the defendant's drug conviction on grounds of insufficient evidence. As the Court explained, the government presented no direct evidence or admissions by Garcia that he had distributed cocaine. Instead, the government relied on agent expert testimony purporting to interpret cryptic telephone conversations between Garcia and a known drug dealer ("girl" = cocaine; "work" = cocaine; "tix" = money; and the like).
This was not enough. Read Garcia in preparing your Rule 29 motion. It contains a great discussion of the "quantum and quality" of evidence required to prove guilt beyond a reasonable doubt, and a nice compilation of other cases in the Seventh and Second Circuits holding that evidence was insufficient to sustain a conviction.