Ill health will no longer prevent Gen Augusto Pinochet answering charges relating to his dictatorship, says investigating Judge Juan Guzman.
For years Judge Juan Guzman has led efforts to try Gen Pinochet
On Monday, an appeals court upheld Mr Guzman's indictment of Gen Pinochet - said to have suffered a recent stroke - on charges of murder and kidnapping.
Gen Pinochet's lawyers have now taken his appeal to the Supreme Court.
But Mr Guzman said a TV interview by Gen Pinochet had undermined claims he is suffering from serious dementia.
In the interview, with a Miami station just over one year ago, the former dictator talked about the past, declaring he was a "good angel", and blaming abuses during his period in power on his subordinates.
"Most of the Chilean people and I myself had a look at that interview and realised that - according to what we thought dementia was - Pinochet is not really a person whose mental faculties are disturbed," Mr Guzman said in an interview with BBC correspondent Clinton Porteous.
He said that, though the Supreme Court has already once declared Gen Pinochet mentally unfit to stand trial, it would "think differently after seeing that interview".
Gen Pinochet has fended off dozens of attempts to see him stand trial on charges relating to human rights abuses during his 1973-1990 military rule.
He now faces charges relating to the murder of one Chilean and the disappearance of nine others.
Mr Guzman said the decision of the former British Foreign Secretary Jack Straw to declare Gen Pinochet mentally unfit to be tried in 2000 was wrong - he was "mentally fit then and continues to be mentally fit now".
PINOCHET TRIAL TIMELINE
October 1998: Police in UK arrest Pinochet on Spanish warrant; long legal battle over fitness for trial
March 2000: Deemed unfit for trial, returns home. Days later effort begins to try him in Chile
August 2000: Supreme Court strips his immunity. Later declared fit to stand trial
July 2001: Charges suspended and later dropped on grounds of health
May 2004: Court strips Pinochet of immunity from prosecution over fresh charges
Dec 2004: Chilean judge indicts Pinochet
Mr Guzman implied Mr Straw was either taken in by Gen Pinochet or had tired of the 18-month battle over the former dictator when he finally decided to release him without charge.
"Mr Straw was fooled or he was 'practical'," Mr Guzman said, laughing.
Mr Guzman told the BBC it was crucial to bring Gen Pinochet to trial.
"Many people were killed, many people disappeared - people have not had the remains of their relatives to honour, to bury, and they haven't been able to mourn," he said.
"Having Pinochet and others held responsible for these crimes at least relieves them in a certain manner, in their sadness that they carry."