I thought I had seen a quote like that also, but I did notice many headlines using the word “guarantee.”
Administration Guarantee of Conviction in Terror Case May Undermine Federal Trial
This is an important question, in the article you posted a link to.
"Sen. John Cornyn, R- Texas, who has sent a letter to the Justice Department and Homeland Security about the terror case, also challenged Holder about what to do if a jury acquits."