"Person of interest" and "suspect" are sometimes used interchangeably. Meaning, one agency might say POI while another says suspect to describe the same person. I think in court the SA meant Tommy was a person of interest in Haleigh's case because if they had enough evidence to officially name someone a suspect, they have enough evidence to arrest, IMO. Not necessarily so for a POI, though. Sometimes a person is a POI just because LE might want to speak with them.
POI describes a person they are interested in for one or more reasons. In some cases, a POI might go on to be charged, in other cases they might be exonerated after LE speaks with them. IOW, it's hard to say exactly why a person would be named a POI but, in the Haleigh case it is obvious LE has wanted information/answers from several people--and thus they are considering them as POIs even without formally naming them as such. Right after the St. Johns River search in April 2010, Hardy stated they had several POIs, though he didn't name any of them. But their naming Misty the key does not necessarily mean they were interested in only Misty and no one else.
For the record, Tommy was convicted of trafficking. He may have narrowly escaped a greater charge (one with a higher minimum mandatory) but he did not escape a trafficking charge so, if the SA said he did, he misspoke. Tommy's 3-year minimum mandatory was for trafficking in hydrocodone. He got a 15 year sentence for that charge, three of those years being mandatory, which means Tommy must serve three years after which time he becomes eligible for early release under Florida's 85% rule.
I think Tommy has a reasonable chance of some type of relief through his appeal. If it can be proven that he was singled out and treated differently than other perps with similar charges coming through the same court, the appellate court could rule in Tommy's favor. Whether or not a person might be viewed as either a suspect or a POI in an unsolved crime cannot be considered in sentencing of another conviction. However, Werter opened his client up for this when he claimed at Tommy's sentencing hearing that Tommy had been helpful in the Haleigh investigation. That opened the door for the SA to give his opinion on just how helpful he felt Tommy had been and in stating his opinion he used the term "suspect."