Malaysia practises a moderate form of Islam but conservative attitudes have been on the rise and the use of Sharia is growing as well. Under a dual-track legal system, thousands of Muslims use it to settle moral and family matters. Non-Muslims are required to follow secular laws that deal with the same matters.
She passes judgment on everything from financial cases to those involving the Sharia concept of Khalwat [unmarried Muslim couples being caught in compromising situations].
But her expertise lies in child custody and cases of polygamy - the Muslim concept of allowing men to marry up to four wives, which is legal in Malaysia.
Judge Shushaidah says there are many factors she considers before, for example, allowing a polygamous union.
"Every case is complex and different," she explained. "You can't generalise Islamic law and say it favours men and treats women badly... I want to correct that misconception."
All those involved in a proposed polygamous marriage are required to be physically present in Judge Shushaidah's court.
"I want to hear from everyone, not just [the] men," she said. "I make it a point to speak with women to find out if they are on board with the arrangement. It is important that they agree to it because if I see any signs that say otherwise then I won't grant permission."
"I am female and I can understand most women would not like the idea. But it is allowed under Islam, and our Malaysian courts have enacted strict laws to govern this."
"A man has to have very strong reasons for wanting another marriage," she said.
"He must show he can look after the welfare of his first wife as well as the women who come after. He is not allowed to neglect the needs of anyone."
Judge Shushaidah added that some wives can be supportive of the idea.
She recalls, for example, a case which involved a seriously ill woman who could no longer bear children.
"She loved her husband and wanted me to grant him permission to marry a second wife. So I did."
She defends her religion's reputation for strict laws by arguing that it is capable of fairness.
But critics and rights groups argue Sharia is often misused.
"We have no objection to Sharia law that doesn't discriminate against women, gay people or social and religious minorities," Asia deputy director of Human Rights Watch Phil Robertson told BBC 100 Women.
"But the problem with Sharia law in Malaysia is that too often it does precisely that.
"Religion is never an acceptable reason to violate international human rights standards of equality and non-discrimination."
For example rights activists were outraged by the recent caning of two Malaysian women convicted of attempting to have lesbian sex, and say Sharia law was misused in this case.
Judge Shushaidah would not address the case, but said: "Caning under Sharia law serves to educate offenders so as not to repeat the act again."
Judge Shushaidah also argues that Sharia does not always rule in favour of men.
"Our law exists to protect women's rights. It looks at their welfare and safeguards their livelihoods," she said.
"Islam holds women in high regard and as judges, we must return to its teachings and maintain worthiness using Sharia."
Her greatest concern lies with Muslim men bypassing strict Sharia court procedures by marrying overseas.
"He wouldn't be bound by Malaysian law if he marries abroad. Some wives actually consent to this to protect their husbands but they don't realise how it works against them," she said. "Our Sharia laws are in place to protect the interests of women and hold men accountable."
Women's groups like Sisters in Islam highlighted a "severe shortage of female representation" in the courts and a "strong sense of patriarchy" in the overall system.
"The Sharia legal context in Malaysia not only selectively discriminates against women, it vilifies them as the cause of social immoralities," said spokeswoman Majidah Hashim.
"State Islamic institutions... have done little to ensure women are accorded due justice. In fact, the recent prosecution of women under Sharia law clearly shows that their voices are alarmingly silenced and access to justice is worryingly stifled."
This makes Judge Shushaidah's appointment a particularly significant one.
"Back in my day, most Sharia judges were men who questioned the need for women in the practice," said Judge Shushaidah.
"I never dreamed of becoming a judge," she admitted. "As a lawyer, I didn't know if I could take on such a senior role that dealt with complicated cases. And as a woman, I felt doubt and fear."
"Sometimes I do feel uneasy. As a woman, I must feel, and I'd be lying if I said I felt nothing. But I am a judge and I have to make sure I am always clear and objective. So in my judgment, I try and address this. I make do with the best evidence I get in court."