There is a possibility that the Sungai Besar parliament seat will only be declared vacant after June 24, said lawyer Mohamad Siddiq Azani.

He added this would help BN avoid a by-election in the constituency, where its late incumbent from Umno won with a razor-thin 399-vote majority in the 2013 general election.

Sungai Besar MP Noriah Kasnon, who is also a deputy minister, was killed in a helicopter crash in Sarawak on Thursday.

"If there is a casual vacancy (vacancy by death) in the Dewan Rakyat, the Election Commission shall establish there is a casual vacancy. This can be done by way of notification/announcement by the EC chairperson.

"An election shall be held within 60 days from the date of notification of the said vacancy by the EC," Siddiq told Malaysiakini.

"Dewan Rakyat has its span of five years and a complete three-year cycle will render the Dewan dissolved; meaning that if any casual vacancy occurs after the complete cycle of three years, no by election shall be held unless upon request by the speaker," he added.

Siddiq noted that the Dewan would soon complete its three-year cycle on June 24, which is 48 days from now.

"If my law and politics reading serves me correctly, BN would not dare declare the Sungai Besar seat vacant before the three-year cycle is completed, because that would result in a by election being held in a seat where it won with just 399 majority in the last election.

"The seat might only be declared vacant after June 24, 2016, which means no by election would be held as the Dewan stands dissolved," he said.

Meanwhile, constitutional law expert Abdul Aziz Bari said that he does not think BN can avoid a by-election through the EC.

"Now the law as it is provided by Article 54(1) of the Federal Constitution simply says that it has to be done if it is still within the first three years," he said to Malaysiakini.

As the oath-taking and the sitting of the 13th Parliament took place after the last general election which was on May 5, 2013, he pointed out that “we are yet to enter the last two years of this Parliament”.

"As such, the EC can't stop it. Now, if the EC or (Dewan Rakyat) speaker can stop or avoid the election, that is quite an untenable proposition; for such could not have been the intention of the framers of the constitution," he said.

The democratic essence of the constitution can be seen from the fact that the speaker is to inform of the casual vacancy even after the three-year period has ended, if such vacancy affects the majority of the sitting government, he explained.

In the 2013 general election, Noriah defeated PAS candidate Mohamed Salleh M Husin.

The deputy minister garnered 18,695 votes while her rival received 18,296 in the Malay-majority Selangor constituency, which has 42,837 voters.