PBI Inspector M Rafiqul Islam, also investigation officer of the case, submitted a charge-sheet before the Court of Dhaka Chief Metropolitan Magistrate in the afternoon.
The charge-sheeted accused are victim’s bother-in-law (Husband’s elder brother) Dr Hasan Ali Chowdhury, 70, his wife Sayedatul Mahmuda Shahin, 64, Shaheen's brother Anas Mahmud Rezwan ,59, and hired killer Maruf Reza, 59.
Earlier in the day, PBI chief Deputy Inspector General (DIG) of police Banaj Kumar Majumder said they finalised the charge-sheet.
While briefing reporters at the PBI headquarters, he said four people were arrested in connection with the murder.
The arrestees gave confessional statements before a court here over their involvement in the killing, the PBI chief added.
He said Sagira was killed due to jealousy of her elder sister-in-law Sayedatul Mahmuda Shahin.
Sagira was shot to death in broad daylight on July 25, 1989 in the capital's Bailey Road area when she was going to Vikarunnesa School by a rickshaw to fetch her daughter.
Sagira’s husband Abdus Salam Chowdhury filed a murder case against some unknown people with Ramna Police Station the same day.
But the trial proceedings of the case remained stayed for 28 years following a High Court order.
Finally, the PBI got the task to investigate the murder on July 17 last as an HC bench ordered further investigation vacating the stay order.