请教专家老师： 

新概念3-35课：

The word justice is usually associated with courts of law. We might say that justice has been done when a man's innocence or guilt has been proved beyond doubt. Justice is part of the complex machinery of the law. Those who seek it undertake an arduous journey and can never be sure that they will find it. Judges, however wise or eminent, are human and can make mistakes.

    There are rare instances when justice almost ceases to be an abstract concept. Reward or punishment are meted out quite independent of human interference. At such times, justice acts like a living force. When we use a phrase like 'it serves him right', we are, in part, admitting that a certain set of circumstances has enabled justice to act of its own accord.

    When a thief was caught on the premises of large jewellery store on morning, the shop assistants must have found it impossible to resist the temptation to say 'it serves him right.' The shop was an old converted house with many large, disused fireplaces and tall, narrow chimneys. Towards midday, a girl heard a muffed cry coming from behind on of the walls. As the cry was repeated several times, she ran to tell the manager who promptly rang up the fire brigade. The cry had certainly come form one of the chimneys, but as there were so many of them, the fire fighters could not be certain which one it was. They located the right chimney by tapping at the walls and listening for the man's cries. After chipping through a wall which was eighteen inches thick, they found that a man had been trapped in the chimney. As it was extremely narrow, the man was unable to move, but the fire fighters were eventually able to free him by cutting a huge hole in the wall. The sorry-looking, blackened figure that emerged, admitted at once that he had tried to break into the shop during the night but had got stuck in the chimney. He had been there for nearly ten hours. Justice had been done even before the man was handed over to the police.

1) 为什么不是are humans ?  instances when 引导定语从句很难理解instances的时间含义？如果说成instances where则能理解，可否？

2) 这个结构quite independent of human interference不会分析，有人说是方式状语，形容词短语作方式吗？但感觉是主语补语，可否？

3) we are admitting 静态动词可以使用进行时吗？must have found 我感觉这里只能理解为从现在的角度去推测，而不能理解为站在过去的角度去推测，不知对否？