ORLANDO, Fla. -

Investigators this week obtained a previously unreleased photograph that documents Casey Anthony?s apparent carefree state of mind 2½ weeks after the state alleges she killed her daughter and dumped her body in the woods.

IMAGES: | | | VIDEO:

The photo was taken on July 4, 2008, as Anthony and her friends walked to a fireworks celebration in downtown Orlando. It shows her with a plastic beer cup held to her lips as she smiles.

Anthony?s partying ways have been well-documented in photographs on social network sites.

But almost all of the party photos obtained by investigators were taken before June 16, 2008, the day her daughter, Caylee, was last seen alive. They would not be relevant to show her behavior in the subsequent weeks.

Only a few previously released photos, taken on June 20 at a nightspot being leased by her then-boyfriend, show her out partying after Caylee was gone.

At least some of those photos were apparently staged, part of a publicity shoot for the nightclub venture. The defense could argue Anthony was just modeling in those photos, not revealing how she was truly feeling.

That left a photographic gap for prosecutors as they prepare to show Anthony's state of mind during the four weeks Caylee?s disappearance went unreported.

Now, with the photo taken by Will Waters on July 4 and provided this week to Local 6, the state has obtained a piece of evidence that fills in part of that gap.

There are surveillance videos and still photos of Anthony at stores and banks, but none of them shows her in a social gathering like the photo from July 4.

Waters said he revealed during his deposition earlier this month that he had taken photos of Anthony, but he was only able to retrieve one from his computers. He said he turned it over to Detective Yuri Melich on Monday.

Anthony, 25, remains jailed on first-degree murder charges. She has pleaded not guilty.

Anthony's murder trial is scheduled to begin in May.

Watch Local 6 News for more on this story.