How far has Apple Inc. (AAPL) progressed in building a driverless car? A criminal complaint filed Monday by the Cupertino, California-based company against an ex-employee alleging that he stole trade secrets from a self-driving-vehicle program may provide a lot of insights, reports Reuters. (See also: Apple Reveals More Details About Self-Driving Efforts.)

The charges filed in the U.S. federal court allege that an employee named Xiaolang Zhang stole secrets of Apple’s ambitious autonomous vehicle project. Zhang was hired by Apple in 2015 to develop software and hardware for the company’s self-driving vehicle project. Following a visit to China in April, he expressed his intentions to work for a Chinese autonomous vehicle startup called Xiaopeng Motors. His supervisor informed Apple's security team which found that Zhang had downloaded the plan for a circuit board from secret databases and had taken hardware from Apple’s autonomous vehicle lab then booked a last-minute flight to to China.

Smuggled Secrets

The BBC quotes the FBI, which said that the data taken by Zhang included "engineering schematics, technical reference manuals, and technical reports," and includes a 25-page "blueprint" for a self-driving car circuit board. Court documents further allege that Zhang admitted to the theft during an interview in June, and he used AirDrop to move the sensitive details from his own device to his wife's MacBook laptop.

Following the complaint, Zhang was arrested by the FBI at the San Jose airport on July 7 and was charged with theft of trade secrets. The formal process of reading of the criminal charging document to him is scheduled for July 27, though he is yet to enter a plea. While a lawyer has been appointed to represent Zhang, there is no further comment from either the defendant or his lawyer as of this writing.

If found guilty, Zhang could face a penalty of $250,000 or may face 10 years of imprisonment.

Apple’s Approach to Build Autonomous Vehicles

While Apple has long kept its rumored project under wraps, the filing of a legal complaint following the fateful development has revealed a few key details about the self-driving car program.

Apple’s complaint alleges that Zhang was shown a “proprietary chip” by his co-workers. He was apparently involved in designing circuit boards used to analyze sensor data, which hints at Apple’s approach to use “sensor fusion,” a technology that combines data from multiple sensors to make it more accurate.

“They think about the whole thing as almost a new artificial intelligence engine. Taking data from a camera and a depth sensor and fusing it together could very well be used with cameras and sensors in phones,” said Sertac Karaman, an associate professor at the Massachusetts Institute of Technology, to Reuters.

Additionally, there have been sporadic instances when Apple’s interest in autonomous vehicles kept hitting the headlines. In 2016, the company requested that U.S. transportation regulators not restrict vehicle testing. It was followed by the company securing a permit in 2017 to test autonomous vehicles in California. That same year, Apple published a report on a software system that can more accurately spot pedestrians. (See also: Apple's Autonomous Car Plans Confirmed by CEO.)