A 30-year-old woman is being held on $1 million bail after she was arrested on Saturday for the seventh time since June on suspicion vandalising a luxury cars.

As yet the attacks in which expensive cars such as Mercedes-Benz models and BMW vehicles have had their sides scratched with a key, appear to be motiveless. It is not known if the owners of the cars are known to the defendant although it would seem the attacks are random.

The latest arrest came over the weekend in the car park of a shopping mall at Westfield Valley Mall. San Jose Police arrested Nancy Chi Ni on suspicion of vandalising three cars parked in the area including a BMW, and Mercedes-Benz, and Honda CRV. Ni will also face charges for committing a felony while on bail.

Police say that on several occasions a pair of sharp scissors has been found on Ni following an arrest.

Earlier in the month Ni was arrested after an officer witnessed her scratching the side of a Mercedes car in Milpitas. The defendant is currently facing 18 charges of felony vandalism, plus a further five charges in separate cases. Another two charges are still pending against the woman.

All of the vehicles damaged in the latest spate of vandalism attacks have all been high end luxury cars.

Ni is reported to drive a black 2009 Mercedes-Benz.