The suspect in the gruesome slayings of five people inside a San Francisco home pleaded not guilty to murder charges Thursday.

Binh Thai Luc, 35, entered his plea to five counts of murder, plus special circumstances of committing multiple murders, robbery, burglary and lying in wait. Luc faces the death penalty if convicted.

Luc appeared nervous and shook his head several times during the 20-minute hearing in San Francisco Superior Court.

“It’s a very emotional thing,’’ said Luc’s attorney Mark Goldrosen, who gently placed his hand on Luc’s back to calm him midway through the hearing. `It is a very difficult thing to stand up there for that long and listen to all the charges.’’

The rail-thin and boyish-looking Luc shuffled in and out of court, his hands handcuffed in front of him and shackled around the waist.

Goldrosen said Luc was a construction worker and a member of a plumber’s union before his arrest.

Judge Samuel Feng reluctantly set bail at $25 million after initially ordering Luc held without the possibility of bail.

But to hold Luc without bail would require prosecutors to disclose enough evidence to convince the judge that Luc likely committed the murders. Prosecutor Sharon Woo said she was unwilling to do that because the investigation was still in the early stages.

“I’m still not comfortable,’’ the judge said in ordering the $25 million bail. Federal immigration authorities also placed a “hold’’ on Luc because he faces deportation if convicted. He would be placed in federal custody in the event he posts bail.