Here is the Prosecutor's memo in the Jessica Lunsford case

Here is the detailed explanation of why they didn't charge the occupants of the mobile home where Couey was staying.

Shortly after Jessica Lunsford was reported missing, uniformed deputies went to the house where the defendant was living with other individuals. There was no reason to suspect anyone in the residence was involved in the disappearance, but questioning was done as part of a general neighborhood canvass. There is no evidence that the defendant knew that Jessica Lunsford was, or had been, in the house. This defendant identified herself, and provided the names of other occupants, but did not inform the deputies that John Couey was living at the residence.

The defendant was aware that there was an outstanding misdemeanor violation of probation warrant for Couey’s arrest, and was aware that Couey was required to register as a sex offender. There is no evidence that the defendant was aware that Couey was involved in the disappearance of Jessica Lunsford. The sole reason that the defendant did not inform the Deputies of Couey’s presence was to prevent his arrest on the warrant and to avoid getting into trouble herself for having him there.
Shortly thereafter, detectives were informed of possible drug activity at the house, and saw someone peeking under the blinds at them. The detectives went back to the house to make further inquiry. There was no probable cause to arrest anyone, or conduct a search. The general nature of the information and sight of someone peeking out at them did not rise to an articulable suspicion to allow for a detention of the occupants of the house, so this second interview was also a citizen encounter.

During this second interview, the defendant again identified herself, and others as occupants, but again failed to disclose Couey’s presence in the house. In response to questions, the defendant stated that those whom she had named were the only persons in the house. During neither the first nor second interview was the defendant asked about John Couey, because investigators had no knowledge of Couey’s existence or his presence in the area. They were only making general inquiry about who was present and if the defendant had any knowledge about the missing child.
After his arrest for the kidnapping and murder of Jessica Lunsford, Couey admitted that he had been living in the house, and was present in the house during the second interview. However, he denies that anyone else in the house was aware that he had kidnapped the child, or that she was being held in the house. There is no evidence to contradict this claim, but Couey’s timeline of the events after he kidnapped Jessica Lunsford leaves open the possibility that she was alive, and in the house, at the time of the first, and possibly the second, interview. Had the defendant disclosed Couey’s presence in the house, the life of the girl might have been saved.

Florida does not have a statute which makes it a crime to lie to a police officer in all situations, nor is there a law which requires a person to disclose the whereabouts of a registered sex offender. The defendant was arrested for violation of Florida Statute 843.02 for obstructing a police officer. According to the probable cause affidavit, the obstructing occurred because the defendant “did by her own admission fail to inform deputies of the Citrus County Sheriff’s Office on at least one occasion that John Couey was, in fact, at said address with the defendant.” The police reports state that the crime occurred because the defendant “lied” to deputies. The lie being the statement that no one else resided in, or was present at, the residence. This is simply a restatement of the grounds cited in the probable cause affidavit.

The courts have addressed the question of whether lying to a police officer constitutes a violation of 843.02. The case closest to this case is Francis v. State, 736 So. 2d 97 (Fla. 4th DCA 1999). In that case, police received a 911 call to a residence concerning a child abuse complaint. When the deputy arrived the defendant said “everything’s okay” and “I don’t need you anymore.” The deputy saw the victim in need of medical assistance and as he attempted to approach the victim the defendant stepped in front of him and attempted to block his path. Francis was arrested and convicted for violating 843.02.
In reviewing the case, the court said

....courts have held that, with limited exceptions, physical conduct must accompany offensive words to support a conviction under the statute. (Cites omitted) ...Words alone may result in obstruction of justice where the officer in question is 1) serving process; 2) legally detaining a person; or 3) asking for assistance.

None of the exceptions noted in Francis apply here. The court went on to hold

....the record reflects that [defendant], in addition to stating these words to [deputy], physically blocked his path when he went over to investigate [victim’s] condition. As such conduct satisfies the second prong of section 843.02, we affirm.

Clearly, it was the defendant’s action, not the words (which were lies) that resulted in the court upholding the conviction in Francis. The cases where false information alone has resulted in a conviction are few, but all of them involve a situation where the defendant was lawfully in custody at the time the false statement was given. An example is Fournier v. State, 731 So. 2d 75 (Fla. 2d DCA 1999) where the defendant, was stopped by police in a citizen encounter. Fournier gave a false name, date of birth, age, and address. When it was discovered that she had given false information she was arrested for violation of 843.02. The court held the arrest to be unlawful and said

The use of mere words can be a violation of section 843.02, when a suspect provides false information to a police officer during a valid arrest or Terry stop.....this rule does not obligate a person to give his or her correct identity to an officer unless that person is legally detained. .....Here, the record provides no evidence that Fournier gave any false information after a legal detention.

In that the defendant was not lawfully detained at anytime, but was being questioned during an encounter, the defendant cannot be guilty of obstruction under this theory.
The alternative theory under which the defendant was arrested is that she failed to advise deputies that Couey was present in the house, while knowing that there was a warrant for his arrest.
The Appellate Courts have rejected this argument also. Beizer v. Judge, 743 So. 2d 134 (Fla. 4th DCA 1999) was a civil case where an individual sued the police for false arrest. Beizer was arrested for obstructing when he failed to inform an officer of certain information. The court stated

...Beizer is being accused of failing to volunteer relevant information regarding the accident. While good citizenship and honesty should have compelled Beizer to tell Officer Judge about Trooper Brinker’s investigation, we can find no authority which makes it a crime to fail to volunteer to an officer all relevant information regarding an incident (accident or crime) within the knowledge of the person reporting it. “No crime is committed by the mere harboring of evil intent not accompanied by an act, or omission to act where there is a legal duty to act.” Thus, there was no probable cause to support a charge of obstruction of justice.

Florida Statutes do require persons to come forward with information concerning the commission of certain crimes. However, there is no statutory provision which requires an individual to notify an officer of the whereabouts of someone for whom there is an outstanding warrant, or of the presence of a sex offender. While the failure of the defendant to tell what she knew may have had tragic consequences, and while there is understandable outrage at the defendant’s failure to tell what she knew, her actions do not constitute a crime under present Florida Statutes.