The short answer to the posed question is that strictly under the law, all proceedings and court papers have to be in the national language i.e. the Malay language.
This is covered specifically under statute as well as the rules governing court procedure. But it was not always the case where it was compulsory to use Malay in the court.
In Malaysia pre-independence, the English language was used in all the courts. Even when the National Language Act was introduced in 1963 making the Malay language the official language of Malaysia, the courts were exempted from making the transition from English to Malay.
However, on 30 March 1990, the National Language (Amendment) Act 1990 came into force which removed the exemption enjoyed by the courts. The new section 8 now reads:
All proceedings (other than the giving of evidence by a witness) in the Federal Court, the Court of Appeal, the High Court or any Subordinate Court shall be in the national language
Provided that the Court may either of its own motion or on the application of any party to any proceedings and after considering the interests of justice in those proceedings, order that the proceedings (other than the giving of evidence by a witness) shall be partly in the national language and partly in the English language.
"Order 92 Rule 1 of the Rules of the High Court
(1) Subject to subrule 2, any document required for use in pursuance of these rules shall be in the national language and may be accompanied by a translation thereof in the English language...
(2) For Sabah and Sarawak, any document required for use in pursuance of these rules shall be in the English language and may be accompanied by a translation thereof in the national language ..."
All court documents now need to be translated into the Malay language, and I am sure every single pupil would have done their significant share of helping lawyers to translate affidavits or other cause papers into Malay. Some of the larger law firms can afford to employ dedicated translators to help with some of the translation. But ultimately, there is still no escaping from doing your own translation work. Having worked hours and hours crafting an affidavit, you then spend as many hours leafing through English-to-Malay dictionaries to translate your work. I always find it ironical that the English portions are marked 'Terjemahan' ('translation' in Malay) when in actual fact, the English portions are drafted first and then translated into Malay.
This compulsory use of the Malay language is relaxed somewhat at the High Court when lawyers are making submissions. Generally, the Registrars and the Judges allow you to file in your skeletal written submissions in English, as well as to orally submit in English. At the subordinate courts, the use of Malay is still more or less compulsory. This means written and oral submissions all have to be in Malay. With my atrocious command of Malay, no surprise then that I do not look forward to my matters at the subordinate courts.
At the appellate courts, being the Court of Appeal and the Federal Court, English is almost exclusively used. I know of certain appellate judges who will tick off Counsel for failing to file in the English translation of the court papers at the High Court level, when these documents are referred to at the appellate stage.
English is also widely-used in the written judgments of the Courts. I would estimate at least 90% of the reported judgments are in the English language.
It is a pity that the court system had to adopt the usage of the Malay language, and could not enjoy the previous exemption. From a commercial point of view, nearly all contracts are drafted in English and it would make sense for litigation arising from these contracts to continue in English. The language used in international commerce is largely English, so again, if parties negotiate for Malaysian courts to adjudicate on a dispute, it would be a plus for the Court language to be in English.
But the use of the Malay language in the Court is necessary as this is a common language understood by all Malaysians. In a criminal court for instance, if charges are being read out to an accused who is unrepresented, the Malay language would largely be understood by all.