As of 691, Di was serving as the military advisor to the Prefect of the capital Prefecture Luo Prefecture, when Wu Zetian promoted him to be the deputy minister of finance. In 692, Wu Zetian’s secret police official Lai Junchen falsely accused Di Renjie, causing him to be locked up. He was later exiled to be the magistrate of Pengze County.
In 696, during the middle of an attack by the Khitan Khan Sun Wanrong against Zhou Prefectures north of the Yellow River, Wu Zetian promoted Di Renjie to the position of Prefect of Wei Prefecture. Later in 697, Di was serving as the commandant at You Prefecture when Wu Zetian recalled him to Luoyang to serve as the deputy head of the examination bureau of government. She soon made Di Renjie the head of the examination bureau. In 700, Wu Zetian made Di Renjie the head of the legislative bureau. By this point, she was said to have respected him so greatly that she often just referred to him as the State Elder without referring to him by name.
Di Renjie was said to be legendary in judging cases and had never judged one wrongly.
When Di Renjie just went into Dali to work, there were many case files. He placed his heart to it and worked for an entire year before clearing it all out, using up 17 thousand men.
The name of God Detective started from then.