Complexity of the law

I read this book called “Judge & Jury” by James Paterson and Andrew Gross. Even though the book was fictional, there was one question that led me to searching for answers since reading (about 10 months ago). Before stating the question I think it will be more helpful if I explain what led to the asking of this question in the book.

Judge & Jury by James Patterson and Andrew Gross is a thriller about a mafia boss on trial. Nick Pellisante was the FBI agent who tacked down Dominic Cavello (Mafia boss) for years.

Dominic Cavello has committed all sorts of gruesome crimes you could imagine; from murder, bribery, distortion, robbery, money laundry, drugs, rape to shooting and killing of two federal officers.

On the trial of Dominic Cavello, Nick pellisante’s biggest obstacle was to convince the Jury that Mr. Cavello was a criminal and the head behind numerous cold case killings. Pellisante in fact witness Cavello shoot and kill two of his federal agents, the problem for Pellisante though was to get witnesses to make sure Cavello gets what he deserved. But even though Cavello was in prison at the time he made sure all Pellisante’s material witnesses are taken down before they could testify against him, thanks to his mafia mob network who will do any thing to make sure the boss is not sent away, well at least not easily.

Pellisante had to later turn to Cavello’s own men who were earlier been sentenced for crimes committed while working for Cavello. Now, Nick Pellisante get this people to testify against the mafia boss by promising reduced sentence terms if they tell the truth about their boss, but the defense counsel will argue that this people are known criminals and liars, who themselves admit in front of the jury that lying was part of their job, even though at least now they are telling all but the truth.

At this point, Nick Pellisante was irritated by Cavello’s attempt’s to interrupt the trial by blowing up the jury bus, sending threat messages to the judge and killing of witnesses and their families through his mob network. Nick went to visit Cavello at prison, out of anger he personally abuse Cavello by physical means with counter threats that his (Cavello’s) threats won’t in anyway stop this trial.

After that Nick was sacked from leading the case, that he was too enthusiastic about the case and that he is taking it personal, he was transferred to a lower FBI department. Out of devastation knowing that he is loosing a case he thought he has already got, knowing that Cavello was guilty of all the charges, knowing that Cavello might get away with shooting and killing two of his closest FBI buddies, Nick decided to take an indefinite career break from the FBI and started teaching a law course at a University where he asked his student’s the following question, I quote;

Can anyone tell me why the law permits law enforcement agents to use deceit (concealing of truth) at the investigative stage, when they are not even sure of a Suspect's guilt, but strictly forbids them from lying during the testimonial stage, When they are absolutely sure that the accused is a Criminal?

One Student responded; “It’s the means to an end” Mapp and United States versus Russell allow the police to use deceptive procedures to obtain evidence, without it they might never make a case. It’s deception for the greater good.”

Nick Pellisante counter questioned; but what if the police have to lie about those procedures during testimony in order to protect their case?

At which point the book didn't go any further about what happens, indeed it’s a fiction or perhaps they leave it to the reader to figure out the rest. I will be very much interested though in finding the answer to this question, for that reason any knowledgeable opinion is very much welcomed!

Peace!