BALTIMORE (WJZ) — A shocking twist in the case of a murdered teen found floating in the Susquehanna River. Prosecutors say they will use a video showing the victim engaging in sex acts with her accused killer.

As Gigi Barnett explains, defense attorneys say the tape could possibly help their case, too.

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Electronic billboards flashed 16-year-old Phylicia Barnes’ name and face across the state.

Four months after her disappearance, investigators found the teen’s naked body floating in the Susquehanna River. Police have since charged Phylicia’s sister’s ex-boyfriend, 28-year-old Michael Johnson, with the murder.

Now, a shocking twist in the case: court documents say prosecutors plan to play a cell phone video of the honor student intoxicated and engaging in sexual relations with Johnson, his younger brother and Phylicia’s sister, Deena Barnes.

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“This, of course is a game changer. So we have to look at it from that standpoint,” said Russell Neverdon, Johnson’s defense attorney.

Neverdon said his office knew about the sex tape. But the 16 minute, 31 second video was recorded and stored on Deena Barnes’ cell phone, and that changes their strategy.

“The problem is that in Maryland, we do have some statutory regulations that say certain people of certain ages cannot indulge in certain activity, particularly in the presence of someone who is supervising them,” said Neverdon.

Prosecutors filed a motion to close the courtroom if the sex tape is played and the defense says it didn’t plan on using the tape to protect the victim’s memory.

State prosecutors say they will not comment about the cell phone video because it’s part of a pending case. Meanwhile, Johnson’s trial is set for mid-January.

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The judge over the case has not yet decided to close the courtroom while the video is being played. That decision should come in a couple of weeks.