Zookeepers attempt tough balancing act with unpredictable animals and visitors

Other possible clues have drawn police attention. A shoe print found on a railing next to the wall of the tiger grotto is being checked against the shoes worn by the three friends. A claw mark was discovered atop the grotto wall, indicating that Tatiana leaped over, a source close to the case said. Stains thought to be blood were discovered on a sign and on foliage between the railing and the wall, the source said.

As part of their criminal investigation, police interviewed the two survivors, as well as a San Francisco woman who said she saw four young men taunting the nearby lions that afternoon.

Mark Geragos, a Los Angeles attorney representing the two brothers who survived the attack, has denied that Tatiana was taunted or provoked in any way. He contends the zoo is orchestrating a smear campaign to divert blame in the incident -- a strategy that could be a preemptive defense against the lawsuits the zoo will almost certainly face.

He also suggested that tigers need no reason to attack. "Has everyone forgotten about Siegfried and Roy?" he asked, referring to the mauling of tiger trainer Roy Horn in 2003.

Even if Tatiana was teased, criminal charges are unlikely, legal experts said.

"You'd have to demonstrate that a reasonable person could foresee that taunting a tiger could result in a death," said Rory Little, a professor at UC Hastings School of Law in San Francisco. "A reasonable person, though, would assume the tigers in a zoo couldn't get out. You can go to the zoo any day of the week and see kids taunting animals."

At zoos across the country, the attack has prompted a second look at safety procedures. In Los Angeles, officials are studying the possibility of adding surveillance cameras.

In San Francisco, the walls of the now-closed big-cat enclosures are being raised from 12 1/2 to 19 feet with panels of thick glass. New signs explaining zoo etiquette -- the equivalent of 'do not disturb the animals' -- are being posted throughout the park. A public address system is being installed. And the zoo last week started adding a 3-foot-tall chain-link fence to bring the walls at two separate polar bear exhibits to 16 feet high.

Built in 1940, the big-cat grottoes are fronted by walls more than 3 feet lower than the height recommended by the Assn. of Zoos and Aquariums. Even so, the organization raised no objections about the safety of the areas in a 2004 inspection, according to San Francisco Zoo officials.