a criminal complaint is likely if negligent or shoddy workmanship is a factor in the balcony tragedy that claimed six lives, US officials have warned.
Mayor of Berkeley Tom Bates (inset right) said such a complaint could not be ruled out.
He confirmed he would ask Alameda County District Attorney Nancy O'Malley to examine criminal proceedings against the builders if there was any evidence of negligence over the catastrophic balcony failure.
The fourth-storey balcony that collapsed and catapulted six students to their deaths was designed and built to cope with almost twice the weight involved.
The revelation came as City of Berkeley planning documents revealed the Library Gardens apartment complex at 2020 Kittredge Street had third and fourth-floor balconies designed to withstand a weight of 45kgs (100 pounds) per square foot.
This is substantially more than the California building regulation that requires a load factor of 28kg (60 pounds) per square foot.
Extensive building code records released by the City of Berkeley have reinforced suspicions that the tragedy is linked to water-related dry rot that caused the critical timber supports to weaken and then catastrophically fail.
The Herald has learned that the investigation is now focussed on the condition and installation of waterproof membranes on the eight timber joists which supported the balcony.
The membranes are designed to protect the timber from water and dry rot.
The Library Gardens complex is a 'podium-style' structure, commonplace in California, in which the bottom storey is concrete built with the four upper floors all timber framed.
Engineers are now examining the recovered balcony joists to see if the protective membrane was somehow damaged.
The balcony from which the students fell, Unit 405, is now in secure storage.
The balcony directly underneath, Unit 305, was removed after it was ruled structurally unsafe.
One Berkeley forensic engineer, Bernard Cuzzillo, who examined scene photos, said the cause was absolutely apparent.
"The evidence is overwhelming. This is failure due to dry rot," he said.
Berkeley Mayor Tom Bates said: "In my view there is a high probability it will be (dry rot)."
The revelation came as the Library Gardens' builder, Segue Construction, rejected any suggestion that two lawsuits against it - of $3m and $3.5m - over improper water-proofing of balconies in San Jose and Millbrae were in any way linked to the Berkeley incident.
Both lawsuits were settled by Segue after residents took cases over wood rot caused by water leaks.
Segue insisted to the Los Angeles Times that the incidents were totally unrelated to the Berkeley incident.