MUST LAW ENFORCEMENT OFFICERS ALWAYS TELL THE TRUTH WHEN QUESTIONING SUSPECTS ABOUT A CRIME

Your favorite Clearwater Criminal Defense Attorney was recently asked an interesting question about the strategy and tactics of police interrogations. Do law enforcement officers have any duty to be truthful while questioning suspects?

Here's the question I received:

My twenty year old son was arrested in Tampa Bay, Florida for being in Possession of a Sawed-off Shotgun. After being questioned for a number of hours, police told him that they had a video which showed him with the shotgun. My son admitted he'd had the sawed-off shotgun. Turns out the Police lied to him about the video. There was no video at all. Can my son's statement be thrown out because the Officer's lied to him?

Degas, Self Portrait

The police in Florida have no duty to be honest in telling someone suspected of a crime what the actual evidence against them is. In fact, police investigators are trained to deceive suspects as to the quantity and quality of evidence and Florida Courts would not view the dangling of a falsehood while fishing for the truth as police misconduct. 

However, there are other consideration which should be investigated that could help your son. First, since your son was in police custody, then he should have been given his Miranda warnings. Did he ask for a lawyer at any time during questioning? If so, then the questioning should have immediately ended.
Further, his treatment and the conditions he endured while in custody should be looked at. For example, in a federal drug case I once made the argument that Post Miranda statements from sixteen Defendants should be thrown out because of the way the Defendants were mistreated with no access to food, water, nor a toilet.
You're right to be very concerned about the charge of Possession of a Sawed-off Shotgun as under Florida law that charge carries a minimum mandatory term of prison. 

Beyond attacking the interrogation of your son, the firearm should be inspected by a Defense firearm expert. Florida does make some exceptions for sawed-off shotguns under that statute; for example, if it can be established that the firearm was an antique or that the firearm is an exception as classified under the Federal law, which Florida recognizes, then a Defense Motion to Dismiss the charge would be successful.

Here's the relevant Florida Statute:
790.221 Possession of short-barreled rifle, short-barreled shotgun, or machine gun; penalty.—

(1) It is unlawful for any person to own or to have in his or her care, custody, possession, or control any short-barreled rifle, short-barreled shotgun, or machine gun which is, or may readily be made, operable; but this section shall not apply to antique firearms.

(2) A person who violates this section commits a felony of the second degree.

(3) Firearms in violation hereof which are lawfully owned and possessed under provisions of federal law are excepted.

Finally, a few years ago I tried a similar case before a jury in Pinellas. The trial was necessary because Pinellas County prosecutors refused to treat my sixteen year old client as the child he was, insisting that he accept a minimum mandatory three year sentence. They did not care that the sentence would have ruined his life. He'd used the shotgun to break into a Doctor's car. During the Jury Trial I argued that since he did not use the firearm as a weapon, but as a tool, he was not guilty of Possession of the Sawed-off Shotgun. The Jury found him not guilty.