Story highlights An expert appeared on CNN's "New Day"

She said Trump movements looked like a "pre-assault indicator"

(CNN) Donald Trump paced and loomed behind Hillary Clinton at times during Sunday night's second presidential debate -- a decision possibly driven by stress during the intensely bitter event, according to body language expert Janine Driver.

"He's decreasing stress by doing all that movement," Driver said of Trump's behavior on CNN's "New Day" on Monday.

And Driver noted that it was Clinton's own "strategic" decision to range freely around the stage and position herself in front of Trump when she was answering questions that contributed to him appearing to lurk behind her because, Driver noted, he had nowhere to go.

"Hillary is going to his side of the stage and standing in front of him," Driver said. "What's he going to do? Sit down? Go to her seat? So he begins to hover ... She's on his side of the stage. I think this is strategic."

"Did Trump interrupt at all when she was standing in front of him?" Driver added. "Not once."

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