He appointed former state Chief Judge Judith Kaye to the case, saying he is being cautious in his approach because of heated politics that have raised concerns about a conflict of interest when he says none legally exists.
Cuomo, often floated as the potential Democratic nominee for governor, told reporters in a teleconference that if Paterson had resigned, the case could have been "moot" and been dropped.
A Marist College poll this week showed Cuomo's approval rating fell 13 points in two weeks as he began investigating Paterson, the Democratic governor who until recently was running for a full term and likely would have faced Cuomo in the primary.
Several polls showed New Yorkers preferred an independent prosecutor for the case, not Cuomo, who said the polls had no impact on his decision to use "an abundance of caution." "There is no technical conflict," he said, now that Paterson has dropped his campaign for governor.
Cuomo was investigating Paterson's role in the case in which a woman accused a trusted Paterson adviser of roughing her up.
Last October, Sherr-una Booker accused Paterson confidante David Johnson of choking her, tearing off her Halloween costume and shoving her against a mirror. She filed a domestic violence complaint but never filed criminal charges.
Paterson has acknowledged that he, two staff members and a member of his state police security detail all talked to Booker before a scheduled family court hearing. He has said Booker called him and he only offered support but did not try to get her to drop her complaint or change her story.
Booker did not show up for the hearing, and the domestic violence complaint was dropped.
Last week, a public integrity commission accused Paterson of violating state ethics laws when he sought and obtained free Yankees tickets for the 2009 World Series and then may have lied about his intention to pay for them.
