"The picture is quite clear in my mind," Mehlis said in an interview published by pan-Arab daily Al Hayat on Wednesday. "I have a very clear picture" of Hariri's assassination.
Hariri was killed along with 22 other people in a massive bombing that ripped through his motorcade in Beirut's seaside Ein Mreisseh district Feb. 14, 2005.
Mehlis said he was looking forward to the day when fingers are pointed in the face of those who commit these crimes.
Mehlis assured that the crime was not exclusively committed by Lebanese nationals, but also by non-Lebanese, adding he has evidence that Lebanese and Syrian security service members have "played a role" in Hariri's assassination.
He said the investigative team had identified the suspects - the four Lebanese generals, adding that the U.N. commission together with the Lebanese had also pinpointed additional suspects on suspicion of involvement in preparing the murder.
The German investigator said he was looking forward to the day when fingers are pointed in the face of those who commit these crimes.
He ruled out any compromise on the Special Tribunal for Lebanon which will start functioning in The Hague March 1.
Mehlis believed that the main thing that could hurt the tribunal is lengthy trials.
On the four Lebanese generals detained since 2005 on charges of involvement in the Hariri murder, Mehlis said: "Legally … they should be handed over to the court."
He recalled that the generals had been arrested on suspicion of their involvement in the Hariri assassination.
"As far as I know, they remained in prison for a period of three years after I left for this very reason," Mehlis told Al Hayat.
He said he strictly believes that it is the responsibility of the Office of Public Prosecution and the Court to decide the fate of the four generals, who include former presidential guard chief Mustafa Hamdan, the former head of the general security department Jamil Sayyed, Ali Hajj, who was internal security forces chief, and the former head of army intelligence Raymond Azar.
Mehlis said Lebanese authorities have the "power to act" to make decisions regarding the detained generals and others arrested in connection with Hariri's killing until the day they are handed over to the court.
He said among the two most important conclusions he had reached with his team was that those involved in the murder belonged to an organized group which has extensive resources and capabilities.