SAN FRANCISCO • Uber says it has no plans to change its background check methods despite being devastated by a deadly shooting spree by one of its drivers.

Uber's chief security officer Joe Sullivan said the ride-sharing company has been working "around the clock" with police since last Saturday night's killings in Kalamazoo, Michigan.

"No background check process would have made a difference in this case because he did not have a criminal history," Mr Sullivan said on Monday.

"If there is nothing on someone's record, a background check is not going to raise a flag."

Suspect Jason Brian Dalton, 45, sat stony-faced as he appeared in court via a videoconference link from jail on Monday while he was formally charged with six counts of murder.

Prosecutors said they were still trying to determine why Dalton began firing - seemingly at random - as he drove through Kalamazoo, possibly picking up passengers along the way.

Kalamazoo's public security chief described Dalton, a former insurance adjuster, as "an average Joe" with no criminal record and had not come to the attention of law enforcement before the shootings.

Dalton cleared a background check to become a driver for Uber on Jan 25, and was at the wheel for slightly more than 100 trips by users of the smartphone-based ride- sharing service during the following weeks, according to Uber.

Dalton had a rating of 4.73 based on a five-star system that passengers use to rate Uber drivers and, "generally speaking", had got favourable reviews, Mr Sullivan said.

Uber received some complaints last Saturday, and earlier, about Dalton's driving but nothing regarding violence or weapons, according to the San Francisco- based company.

Uber automatically suspends drivers after accusations of violence, but opts to discuss driving gripes because "we get a lot of complaints about bad driving and they are not all accurate", Mr Sullivan said.

While Uber does not have fingerprints of aspiring drivers checked against US criminal databases, it obtains extensive personal information including social security numbers to dig into records on local, county and national levels, according to the company.

"A background check is just that; it does not foresee the future. After an incident like this, we all struggle for answers," said Uber safety advisory board member Ed Davis, a former Boston police commissioner.

Uber also said it did not plan to introduce in the United States a "panic button" being tested for the company's smartphone application in India to let riders quickly connect with police. "People with smartphones [in the US] could just call 911," Mr Sullivan said.

AGENCE FRANCE-PRESSE