(delivering the JUDGMENT of the court): These appeals arise from the High court's dismissal of the four appellants' applications for leave to issue writs of habeas corpus. The respondents in each case are the same. The habeas corpus application by the appellant Teo Soh Lung was made on 22 April 1988. The applications by the other three appellants were made on 27 April 1988. The High court heard the applications by Chng Suan Tze ('Chng'), Kevin de Souza ('de Souza') and Wong Souk Yee ('Wong') together; Teo Soh Lung's ('Teo') application was heard separately by the same judge. The appeals were argued before us in similar fashion but Teo's appeal was argued first over four days from 19—22 September 1988; the other three appeals took two days on 24 and 25 October 1988. Extensive arguments were raised before us in all these appeals, and for reasons which will soon become apparent, we have decided to give our decisions in all four appeals in a single judgment.The facts

Teo, de Souza and Wong had been arrested together with 13 others on 21 May 1987 during a security operation launched by the Internal Security Department ('ISD') of the government, pursuant to s 74(1) of the Internal Security Act (Cap 143, 1985 Ed) ('ISA'), for being involved in a marxist conspiracy to subvert and destabilize the country to establish a marxist state. It appears from a press statement in an affidavit filed in these proceedings that one of those arrested, Vincent Cheng, who is also alleged to be a central figure in this conspiracy, subsequently said on television that he was setting up a marxist network and systematically infiltrating religious and other bodies and building up pressure groups for confrontation with the government. According to him, this would start with peaceful protests, escalating to mass events, 'leading to public disorder and maybe even rioting, bloodshed and violence'. On 19 June 1987, the Minister of Home Affairs ('the Minister') made detention orders pursuant to s 8(1)(a) of the ISA directing that Teo, de Souza and Wong be detained for one year with effect from 20 June 1987.

Chng, on the other hand, was first arrested on 20 June 1987. She was subsequently served with the Minister's detention order made under s 8(1) of the ISA on 18 July 1987 providing for her detention for one year with effect from 19 July 1987. Pursuant to s 11(2)(b) of the ISA, all four appellants were served with statements pertaining to the grounds and allegations of fact on which their detention orders were based.

In Teo's case, the statement stated as follows:

Grounds on which a detention order is made

Between 1984 and May 1987, you acted in a manner prejudicial to the security of Singapore by being involved in a marxist conspiracy to subvert the existing social and political system in Singapore, using communist united front tactics, with a view to establishing a marxist state.

Allegations of fact

(1) That you facilitated the infiltration of the Workers' Party in 1984 by a group of marxists after discussions with Paul Lim Huat Chye, Tan Wah Piow's fellow marxist, and other activists. You also actively assisted them in their efforts to make use of the Workers' Party as a vehicle to further the marxist cause.

(2) That you and Tang Fong Har made use of the Law Society of Singapore as a political pressure group at the suggestion of Paul Lim Huat Chye.

On 15 August 1987, pursuant to s 11(1) of the ISA, Teo submitted written representations to the advisory board. In her representations, she protested her innocence, denied any complicity in the marxist plot, denied that she was a marxist or a member of the Communist Party of Malaya and claimed that she was legitimately exercising her civil and political rights. She also expressed her belief that her arrest and detention '(might) be intended to prevent (her) from participating in politics'. As for her links with Tan Wah Piow and Paul Lim, who are also alleged to be key figures in the marxist conspiracy, the a