The inquest heard one of the Tsim Sha Tsui shoot-out victims, off-duty constable Tsui Po-ko, had probably been spying on the movements of several political figures and had been observing shift changes at the PLA's Gun Club Hill Barracks. Analysis of seven underpasses suggested the one in Austin Road, where the shoot-out occurred on March 17 last year, was the best for someone planning an early morning ambush. The Testimony Detective senior inspector Yau Nai-keung told the inquest that information about 20 to 30 Beijing loyalists appeared in Tsui's diary and notes. He believed they were followed by the constable between March 2005 and January last year. 'The purpose of my investigation into these notes was to identify the persons or organisations in which Tsui was interested. We interviewed these persons to verify the information and try to figure out Tsui's motive. 'The longer the duration of observation, the bigger the threat to the safety of the target, if there had been any vicious motive behind it.' From evidence concerning a stolen light goods vehicle found in Kwun Chung Street and a motorcycle in Tung Chung, Inspector Yau tried to reconstruct the movements of Tsui on the night of the shoot-out: 'He could arrive at the underpass in 33 minutes after he left Tung Chung police station at 11.48pm on the night of March 16.' He also assessed the environment of the underpass: 'Two characteristics of the underpass in Austin Road were identified - the mirrors and the visiting book.' Today The Coroner's Court will hear experts' evidence on criminal investigation analysis regarding criminal behaviour. The shoot-out investigators will testify about the vehicles Tsui allegedly used on the night of the shoot-out. Witnesses: Two police officers and James McNamara from the Federal Bureau of Investigation.