He was held from the capital's Segunbagicha around Wednesday noon, Dhaka Metropolitan Police's Deputy Commissioner Masudur Rahman told bdnews24.com.
The first war crimes tribunal of Bangladesh sentenced BNP MP Salauddin Quader to death for his Liberation War-time atrocities.
However, the convict's family claimed the verdict had been 'leaked' before it was delivered in court. They had produced a copy of it published on a website.
The tribunal had filed a General Diary over the reported leak.
After a probe, a case was filed accusing three persons under the Information Technology Act.
Police seized two computers and a number of documents from Fakhrul Islam's Kakrail office on Oct t.
The tribunal's employee Nayan Ali and typist Faruk Hossain were arrested and remanded in this connection.
Nayan issued a confessional statement before the court in which Faruk's association with the alleged leak had come to light, according to police.
Detective police say one of Fakhrul's associates had enticed Nayan to take a copy of the verdict's draft from the tribunal's computer. Tribunal employee Faruk had helped him in doing this.