Super Deduction

Single Woman and Blonde Man\On a snowy winter night at No. 68 Jingxi Road, inside the door of a house, a single woman was murdered. The crime occurred at around 8 PM that night.\As soon as the police arrived at the scene, they began a thorough investigation and discovered that in the room, the gas stove was red from the heat, the room was so hot that sweat streamed down, and the electric lights were still on. However, the tightly closed windows were only half-covered by curtains.\At this time, a nearby resident, a young man, provided the police with eyewitness evidence as follows:\Around 11 PM last night, I saw the murder happen. Although my room is 20 meters away from the scene, I noticed that the perpetrator was a blonde man, wearing black-rimmed glasses, and also had a beard.\Based on the clues he provided, the police arrested the blonde boyfriend of the victim.\In court, the lawyer of the blonde suspect confidently defended him and asked the eyewitness: "Young man, you happened to see the perpetrator by the window at the time of the crime, correct?"\"Yes, because the window across from mine was transparent, and that night the victim's curtains were only half-drawn, so I could clearly see the perpetrator's face from 20 meters away.\"At this point, the lawyer confidently said: "Your Honor, what this young man said is all lies, which is perjury. In my judgment, he is the prime suspect, because only after the crime did he adjust the victim's curtains in order to escape. He also provided false testimony to the police to cover up his own crime."\As a result, after examination, it was proven that the lawyer's inference was correct. Do you know how the lawyer reasoned?