Two teenagers pleaded not guilty Friday to murder and arson charges for the strangulation death of a Castro Valley woman whose home was also set on fire.

Christian Birdsall, 16, and Cody Nicosia, 18, have both been charged with the special circumstances of committing a murder during the course of a robbery in connection with the Oct. 17 death of 58-year-old Barbara Latiolais.

Latiolais' body was found at about 12:15 a.m. on Oct. 18 after the house in the 2400 block of San Carlos Avenue was set on fire, Alameda County Sheriff's spokesman Sgt. J.D. Nelson said.

Describing the crime as "the kind of case that fears and nightmares are made of," Nelson said an investigation determined that Birdsall and Nicosia had a plan to steal guns and money from the home that Latiolais shared with her longtime boyfriend, retired San Francisco firefighter Michael Rice, 60.

Birdsall knew the couple because he's a distant relative of Rice and had done some yard work for them, Nelson said. The two teens planned their crime for Oct. 17 because they knew Rice was out of the state at that time, he said.

Birdsall attended Redwood Continuation High School in Castro Valley and was living with Nicosia, who graduated from Castro Valley High School in June, and Nicosia's father in Hayward, according to Nelson.

Sgt. Dave Dickson, who led an intensive investigation in which 20 deputies worked up to 18 hours a day, said the two teens arrived at the home around 8 a.m. on Oct. 17 and waited for four or five hours for Latiolais to leave, but when she continued to stay in the house, they decided to go inside and "made the decision to kill her."

Latiolais let Birdsall inside after he knocked on her door and said he wanted to do additional yardwork, Nelson said.

Birdsall then opened the back door for Nicosia, who hid in the house for nearly an hour before grabbing Latiolais from behind and choking her to make her pass out.

The two teens next took guns, rare coins, jewelry and cash from the house and when they heard Latiolais making noises that indicated she was still alive they took a rope and strangled her to death.

Birdsall and Nicosia then drove off with the loot in the couple's Volvo and had a late lunch at a local restaurant, according to Nelson.

Nelson said Birdsall and Nicosia later realized that "they left a dead body and evidence behind" so they returned to the home at about 10:30 p.m. that night to set the house on fire in an attempt to cover up evidence in the case.

Nelson said investigators got a break in the case on the morning of Oct. 18, when Birdsall drove the Volvo to Redwood Continuation High School but realized after his first class that he probably shouldn't be using the car any longer.

Birdsall then left the campus to drive the car to nearby Brookdale Avenue, where he left it, according to Nelson. He said a witness saw Birdsall leaving the car and later gave authorities a description of him.