Summary: A grand jury isn't anything new in an investigations, it's how you get subpoenas. What is interesting is the conflicting accounts coming out of mainstream media on what they are searching for. If the FBI, CIA, NSA, and DIA can't find collusion what makes you think Rob Mueller can? If CNN is to be believed, it does look like a witch hunt given their write-up suggesting they are just looking for any crime they can get their hands on. Sources: https://www.reuters.com/article/us-usa-trump-russia-idUSKBN1AJ1SW https://www.wsj.com/articles/special-counsel-mueller-impanels-washington-grand-jury-in-russia-probe-1501788287 http://www.cnn.com/2017/08/03/politics/mueller-investigation-russia-trump-one-year-financial-ties/index.html
