Head constable Chandrapal, a close aide of Uttar Pradesh minister Gayatri Prajapati, surrendered before Lucknow police on Monday.
Additionally, Prajapati, who is evading arrest, on Monday failed to get relief from the Supreme Court, which expressed unhappiness that its order on lodging of FIR against the SP leader was being given a "political colour".
A bench headed by Justice AK Sikri, clarified that it has only ordered the Uttar Pradesh police to lodge an FIR against Prajapati in cases of alleged gang rape and attempt to rape a woman and her daughter and is not monitoring these cases.
The minister can approach the court concerned for appropriate relief, the apex court said while rejecting Prajapati's plea for recall of its order for lodging an FIR against him.
The apex court had on 17 February directed the UP Police to lodge an FIR against Samajwadi Party (SP) leader Prajapati, and asked it to submit an action taken report regarding the incidents in eight weeks, in a sealed cover.
The Bench We have simply directed registration of an FIR and investigation in these cases...but now a political colour is being given to this order. It is unfortunate.
"Let the police investigate this matter and say whatever they want," the apex court said.
Prajapati, whose opponents have used the issue in electioneering in poll-bound state to attack him and his party, has cried foul, alleging that it is a "politically motivated" case as the complainant is affiliated to the BJP.
The apex court's direction had come on a petition by a woman who had alleged repeated gang rape by Prajapati and others, and sought the court's order for lodging the FIR.
The alleged offence was first committed in October 2014 and was repeated till July 2016, but when the accused tried to molest the minor daughter of the victim, she wrote to the state DGP in October 2016, requesting the officer to take action.
(With inputs from media agencies.)