The Wall Street Journal reports that special counsel Robert Mueller has convened a grand jury to investigate purported collusion between the Trump campaign and the Russians to affect the outcome of the 2016 presidential election.

For its part, the Trump people have hired a phalanx of high-priced lawyers. One of them, special counsel to the president Ty Cobb, has announced that "The White House is committed to fully cooperating with Mr. Mueller."

I sure hope Ty was kidding. Cooperation with Mueller's lynch mob is the last thing Trump or any of his people should do. But, just in case Cobb meant what he said, let me offer him some free advice.

Ty, you don't know me. No reason you should. I'm not a high-powered New York or Washington lawyer. A classy guy like you would sneer at my low hourly rate and my cheap, ill-fitting wardrobe. If I ever showed up at your private club, you would undoubtedly rub your cigar out on my forehead and have me escorted off the premises for vagrancy.

But, please, listen up. I'm speaking to you as one who spent more than 20 years as a prosecutor conducting federal and state grand jury investigations and another 20 years as a defense lawyer representing targets of grand juries. As a prosecutor, I interrogated hundreds of witnesses under oath for thousands of hours and presided over the return of grand jury indictments and presentments resulting in thousands of felony charges. So listen carefully.

The absolute last thing someone in your client's position should do is cooperate with Mueller. For the target of a grand jury investigation, cooperation is a sucker play guaranteed to result in disaster. If your client is a so-called person of interest or potential target, never, ever allow him to testify before the grand jury. Same thing for giving a statement to an investigator. It's a trap, plain and simple.

Even if the prosecutor can't prove that your client committed the crime supposedly being investigated, he will be charged with obstruction of justice or some similar offense for providing false information to agents or false swearing. This will happen as surely as night follows day.

And I don't care if your client is Mother Teresa telling the absolute truth. All a highly motivated prosecutor has to do is have some lying sleazebag contradict her testimony, and Teresa will leave the courthouse in handcuffs.

Is this unfair? Of course, but it happens all the time even under the best of circumstances. But, as you know, your client is not being investigated under optimum conditions.

In addition to supposedly colluding with the Russians, your  client is facing investigation for obstruction of justice because of a conversation that he purportedly had with former FBI Director James Comey about the FBI's investigation of retired Gen. Michael Flynn. Put aside the law-review nicety that it is legally impossible for a president to obstruct justice in this manner. Keep your eye on the ball. If Trump gives a statement to an agent or testifies before the grand jury, all Mueller will have to do is have Comey, his friend and former colleague, provide contrary evidence. And whose testimony do you think Mueller will credit?

Predicting the winner of that swearing contest becomes easier if one keeps in mind that Mueller has hired a team of assistants, many of whom either supported Hillary Clinton's candidacy or worked for the Clinton Foundation. And given the hyperpartisan rancor that pervades Washington as well as the Clintonistas' naked determination to undo the results of the election, your client's prospects become bleak indeed.

Ty, it is your duty to protect your client by every legal and ethical means. But beyond the usual duty of a lawyer to serve his client's interest, keep in mind that there are more than 60 million very angry pro-Trump voters who are watching to see if the immutable and permanent Washington political class will effectively disenfranchise them by using the criminal justice system to reverse the outcome of the election. In that sense, your client's cause is their cause, too.

George Parry is a former state and federal prosecutor practicing law in Philadelphia.