Masood was shot dead in front of her house in Bhopal on August 16, 2011.
In a statement before the special CBI judge Rajiv Ayachi, Irfan said he and Tabish passed by Shehla's house on a motor- bike six times earlier but he (Irfan) could not muster the courage to commit the murder.
On August 16, 2011, Tabish shot Masood with a country-made pistol when she came out of the house and was entering her car.
According to Irfan, he too was present at the time. After the killing, he asked Tabish to sit on the back seat of the motorbike and they fled from the area.
He said he took part in the act as he needed money for his sister's wedding.
After the killing, the duo went to co-accused Shaquib Danger's house where he learnt from the TV news that the victim was Shehla Masood.
Danger has been accused of arranging weapons. Irfan said that Danger paid him Rs 8,000 in two instalments before the killing and Rs 35,000 afterwards.
The other two accused are Bhopal-based interior designer Zahida Pervez and her close friend Saba Faruqui. According to CBI, Zahida planned the murder as she was jealous of Masood's growing proximity to former BJP MLA Dhruv Narayan Singh.