The attorney for Bulos Zumot launched a fresh attack Monday against a cell phone expert who helped the Palo Alto police track the locations of Zumot's and Jennifer Schipsi's phones in the days and hours before Schipsi's death.

Mark Geragos attempted Monday to discredit the testimony of Jim Cook, who testified earlier in the trial about how he used phone data from AT&T and a list of the company's cell tower locations to track the locations of Zumot's and Schipsi's phones in the days before Schipsi's body was found in a burned Palo Alto cottage.

Zumot, who formerly owned Da Hookah Spot in downtown Palo Alto, was arrested Oct. 19, 2009, four days after the fire, and charged with murder and arson.

Earlier in the trial, Cook pointed to a series of calls and text messages on both iPhones and used the cell tower information provided to him by AT&T to map out the locations of the calls. He said the two phones appeared to have been traveling together in the hours before the cottage fire and that they both seemed to be traveling between Palo Alto and San Jose and back.

Police believe Zumot killed Schipsi well before the fire and then used her phone to send messages to her friends.

Geragos on Monday tried to debunk Cook's explanation by pointing to AT&T data showing cell towers as disparate locations used for the same phone call. In some cases, raw data from the company indicated that two of Schipsi's calls relied on cell towers in Palo Alto and San Jose, respectively. Phone records showed that the calls were made six seconds apart.

"You think you can get from Palo Alto to San Jose in six seconds?" Geragos asked Cook under cross-examination.

"I don't know your method of transportation," Cook replied.

Geragos then pointed to two other calls that Schipsi apparently made on Sept. 9, 2009. The calls, made two hours apart, appeared to have used towers in Hawaii and in Palo Alto. Another document showed two of Schipsi's phone calls made 4 seconds apart -- one using a Palo Alto cell tower and another using a San Mateo tower.

He asked Cook if its feasible that Schipsi traveled from San Mateo to Palo Alto, a distance of about 18 miles, in 4 seconds or if that also "depends on your mode of transportation"?

Cook said he relies on more than just raw phone-call data from AT&T before he creates his maps. He also said when he encounters major deviations, such as the one Geragos singled out, he confers with AT&T and looks at additional information before reaching a conclusion.

"That's not how you'd map it," Cook told Geragos after Geragos showed the jury a Google map showing towers in San Jose and Gardnerville, Nev. -- towers that according to AT&T data were used on the same call.

"That's not how you would map it," Geragos responded. "That's because it would show your theory doesn't work."

Cook's testimony is a key components of prosecutor Charles Gillingham's case against Zumot, who had a volatile two-year relationship with Schipsi. The two fought the night before the fire, according to witness' testimony, and Zumot had just returned from his court-ordered domestic violence course in San Jose when the Addison Avenue fire was reported.

During his opening remarks at the beginning of the trial, Gillingham showed jurors maps showing the location of the two cell phones in the hours before the fire. Geragos responded during his own opening statement by calling the prosecution's evidence "hocus pocus" and arguing that a cell phone cannot be tracked in the manner Gillingham described.

Geragos reemphasized Monday that Cook is relying on a method that had not been reviewed or certified by any professional organization.

"You're just doing something you came up with," Geragos said. "There is no peer review, there is no National Association of Cell Phone Trackers and Mappers.

"Clearly, your theory wouldn't make sense if you mapped it this way," he added.

Cook stepped down from the witness stand after almost two days of intense questioning by Geragos. Judge David Cena indicated he could be recalled later in the trial.