1. witness
n.目击者，见证人（＋of/ for+名词）
v.目击，亲眼看见；作证，证明
The police found the witness to the murder case.警察找到了那件谋杀案的目击者。
I was called as a defense witness.我被传唤作被告证人。
He gave false witness in the court.他在法庭上作了伪证。
Did you witness the accident?你亲眼看到那次事故了吗？
He witnessed the truth of my statement.他证明我的陈述真实。
He witnessed to having seen the man enter the room.他作证说看到那个男人进了那个房间。

2. case
n.事例；场合；事实；案件；病例
固定短语：As is often the case,…..是常有的事；in any case 无论如何，反正，不管怎样；in case在情况下，万一；以免；免得；以防万一；in case of 万一； in no case= never决不
He is an obvious case of somebody whose parents expect him too much.父母对他期望过高，他就是一个活生生的事例。
Can you think of a case where this word can be used? 你能想到这个单词所用的场合吗？
Is it the case that he has lost all his money? 他丢了所有的钱属实吗？
Who is in charge of this case of murder? 谁负责这个谋杀案？
The doctor explained her case to her family.大夫把她的病情告诉了她的家人。
As is often the case, he was punished to copy his exercises ten times.他被罚抄作业十遍是常有的事。
In any case, do your best. 不管怎样，你一定要尽力。
In case anything important happens, please call me up.万一有重要的事情发生，请打电话给我。
You’d better take a taxi in case you are late for the meeting.你最好打的士去，以免开会迟到。
It may rain, you’d better take an umbrella in case.天可能要下鱼，你最好带把伞以防不测。
In case of fire, call 119.万一失火的话，请拨119。
In no case should we give up when we are in face of danger.面对危险时我们决不能放弃。

3. search
vt.后接人或地方作宾语。表示“搜身，搜地方”如：
I was searched by the customs officer at the airport.在机场海关官员搜了我的身。
The police were searching the forest for the missing boy.警方在树林里寻找那个失踪的男孩。
vi.后接for 表示“寻找”
The police were searching for the missing boy, but they haven’t found him so far.警方一直在寻找那个失踪的男孩，但到现在为止还没有找到。