A three-judge bench headed by Justice Dipak Misra, however said, though the appointment of the SPP is "bad in law", it does not warrant "de novo" (fresh) hearing of appeals of the convicts, including the AIADMK chief.
"Tamil Nadu has no authority to appoint respondent number 4 (Singh) as Special Public Prosecutor," the bench also comprising justices R K Agrawal and Prafulla C Pant said, adding that it does not concur with the findings of Justice Madan B Lokur that fresh hearing on the appeal be conducted before the high court.
The bench also allowed DMK leader K Anbazhagan and Karnataka to file written submissions in the high court by Tuesday.
It said that high court can go ahead and pronounce the verdict after considering the submissions of Anbazhagan and the state in the matter.
Dealing with the legal provisions on the appointment of SPP, the bench said Singh's appointment was only meant for the trial in lower court.
On April 22, the apex court had reserved its judgement on the issue of legality of appointment of Singh as SPP and noted that his appointment prima facie appeared to suffer from irregularities but it will not allow the de novo hearing before the high court.
The bench had also allowed the DMK leader, who had filed a petition seeking removal of Singh as SPP in the case, to file his written submission before the high court which will be considered by it before passing its judgement on the appeal by Jayalalithaa and others.
The matter was referred to the larger bench on April 15 when a bench comprising justices Madan B Lokur and R Banumathi had delivered a split verdict.
Earlier, Justice Lokur, heading the two-judge bench, had allowed the plea of Anbazhagan and ordered a fresh hearing on the AIADMK chief's plea against her conviction, saying the appeal proceedings, conducted so far, have been "vitiated".
However, Justice R Banumathi had differed with Justice Lokur and held that the SPP was duly authorised to represent the state before the Karnataka high court.
Jayalalithaa, her close aide Sasikala and two of her relatives were, on September 27 last year, sentenced to four years of jail term for accumulating wealth disproportionate to known sources of income in an 18-year-old corruption case.
The Special Court, which had held Jayalalithaa and three others guilty of corruption, had also slapped a fine of Rs 100 crore on the AIADMK chief and Rs 10 crore fine on each of the three other convicts.
On October 17, 2014 the Apex court had granted conditional bail to Jayalalithaa.
The Apex court on April 17 had extended the bail of Jayalalithaa, which was to expire on April 18, till the disposal of her appeal in the Karnataka high court.
A bench of Chief Justice H L Dattu had also granted the high court time till May 12 to decide the AIADMK chief's appeal, which will be subject to a decision by a three-judge bench of the Apex court.
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