DiNozzo's choice was based on input from actual federal agents.
"For months the writers have been discussing with me (and Michael) what would motivate Tony DiNozzo to leave his NCIS family," Glasberg said. "It would have to be something so powerful no one would disagree. It couldn't be another job. It couldn't be about money. I even struggled with it being for another relationship."
"Hours, days, we sat in the writers room talking. Being a field agent is dangerous. And, if you're suddenly a single parent, do you continue to take that risk every day? Or, does having a child change everything? Based on all of our research, talking to actual federal agents and law enforcement officers, it certainly does change things. And, now Tony would do anything for that little girl. Anything."