The difficulty of proving its efficacy is clearly one of the biggest stumbling blocks.
The older kids learn something about the difficulty of proving a negative.
Whether the difficulty of proving intent helps other defendants remains to be seen, of course, and every case is different.
A lawyer familiar with the decision cited the difficulty of proving significant damages; Insys was not a big fish yet.
Skyworks' strategy is also driven by the difficulty of proving a material adverse change, or MAC, claim in Delaware.
Also, the difficulty of proving complicity in laundering meant that the Hong Kong authorities pursued individuals rather than financial institutions.
Justice Department officials say that it reflects the difficulty of proving fraud — and not a lack of prosecutorial zeal.
He sued, but then faced the difficulty of proving history, thereby providing some sort of comfort to the late politician's family.
As in the Manning case, the firewall turned out not to be the First Amendment but the difficulty of proving intent.
So far, the cases have received little attention and have been hampered by the difficulty of proving that many participants were knowingly involved in deceptions.
The D.A.'s office, possibly foreseeing the difficulty of proving guilt beyond a reasonable doubt, offered Jackson a plea bargain: life in prison without the possibility of parole.
