Chennai, April 27: The Supreme Court today scrapped the appointment of a prosecutor who would have appeared before Karnataka High Court when it decides on Jayalalithaa's appeal against her assets-case conviction next month, in a directive virtually seen as a legal setback to the AIADMK chief.

A three-judge bench ruled that Bhavani Singh's appointment as public prosecutor by the Tamil Nadu government's directorate of vigilance was "bad in law".

It also said the hurry with which the appointment letter had been issued betrayed the ruling AIADMK's "anxiety".

The top court said the written submissions of Singh, accused of openly leaning in favour of the accused at the trial court and the high court, too, wouldn't be considered by Karnataka High Court judge C.R. Kumaraswamy while deciding on the appeal.

Instead, the top court directed the judge to take into consideration the written arguments of DMK general secretary K. Anbazhagan and the Karnataka government, which alone was authorised to appoint the prosecutor in the case.

The DMK today filed its written arguments in the high court. The Karnataka government would file its arguments tomorrow.

In September last year, the trial court in Bangalore, where the case had been shifted to ensure an unbiased trial, had sentenced Jayalalithaa to four years in prison in the assets case. The court also fined her Rs 100 crore.

Jayalalithaa had appealed to Karnataka High Court, where Singh - armed with the letter of appointment from the Tamil Nadu government - appeared as prosecutor from October to March this year, when the court reserved its verdict.

Anbazhagan had challenged Singh's appointment as prosecutor in the high court, contending that his role was restricted only to the trial court. The matter had reached the apex court, which gave its verdict today.

The top court ruled that the Tamil Nadu government had no right to appoint Singh the special public prosecutor to appear in Karnataka High Court. It said the appointment "was a manifestation of the (AIADMK) government's anxiety about the future", in what was virtually a rap on the Tamil Nadu government.

The top court also said there was no need for the high court to hear the case afresh, since its judgment has been reserved.

The bench laid down guidelines on how the high court judge should decide the merits of the case, saying "the filament of reasoning will naturally flow from a dispassionate viewing of the evidence".

It advised the judge to be vigilant about the "corroding effect of corruption" and the "gravity of the offence" against the accused. "It is the duty of the judge to make a complete and comprehensive evaluation and appreciation of the evidence in its entirety before rendering his judgment," the bench said.

A former advocate general said such a directive "virtually knocks out" whatever the defence has argued before the high court, since the trial court's verdict would now become the benchmark for the high court judge.

"For all purposes, Jayalalithaa is staring at a negative verdict from the high court as well," said the veteran lawyer.

"We are thinking of filing a review petition," a senior AIADMK lawyer said.

The verdict came on a day DMDK leader Vijayakanth took along with him representatives from the DMK, BJP and the Congress to meet Prime Minister Narendra Modi to present a petition against the construction of another dam on the Cauvery by Karnataka.

The development marked a rare show of Opposition unity in Tamil Nadu ahead of next year's Assembly elections.

Sources said in the coming months, the political discourse in Tamil Nadu would be decided by what Justice Kumaraswamy pronounces in mid-May.