Few and fortunate are the faithful followers of Jesus who have not, at some point, been subjected to a massive guilt-trip by an enthusiastic, self-styled preacher-“evangelist”, roundly scolding them for the inadequacy of their “witnessing.” This peremptory judgment is usually followed by an offer of reprieve, in exchange for submitting to lessons on “effective witnessing.” The perpetrator of the guilt-trip then proceeds to outline a series of propositions (complete with chapter-and-verse proof-texts) which are to be carefully committed to memory, and retrieved on cue to demolish the defenses of a hapless target, thus fulfilling one’s supposed duty to “obey the Great Commission.” I am quite certain that what the Lord had in mind when giving that assignment was quite different from this (only slightly) more civilized version of collecting scalps! The only thing sadder than this abuse of the clear admonition of Scripture, is its deleterious effect on both the gullible “student” and his (not-so-unsuspecting) victim.
Let’s get one thing straight: Jesus did tell his disciples (Lk.24:48), “You all are witnesses of these things (the fulfillment of ancient prophecies by means of his resurrection)”, and later (Ac.1:8) “You all will be my witnesses.” Both of these statements are cast, not in the imperative (command) mood, but in the indicative: a simple statement of fact. A person who has observed or participated in any event is, by definition, a witness.
“Witness” and “testimony”, both translations of martus (the person) and its related words, martureo and marturomai (verbs), marturia, and marturion (nouns referring to the content of the testimony), are, first of all, legal, judicial, courtroom words. In antiquity, as in the first century, and still today, it is incumbent upon a “witness” that he report, as accurately as he is able, what he has personally experienced or observed – no more and no less. He does not volunteer information, but simply answers questions. Mere “hearsay” evidence is peremptorily thrown out of court!
In his first letter, John outlines this principle ably and succinctly (1:3) – “It’s what we have seen and heard, that we are reporting to you!” Luke, who did not have the privilege of first-hand experience, says (1:2) that in his account, he relied upon the “original eyewitnesses” for his information. He does not call himself a witness, but a researcher-organizer of the testimony of others. Paul, on the other hand, repeatedly refers to his own experience, in both oral and written testimony.
There are New Testament accounts of purported “witnesses” whose “testimony” was pre-programmed by others: the false witnesses enlisted by the ecclesiastical authorities to testify at Jesus’ trial (Mt.26:59-60; Mk.14:55-58); the false report concocted by those same authorities to deny his resurrection (Mt.28:11-15); and the men brought in for the lynching of Stephen (Ac.6:11-15). Which sort of company do you prefer to keep?
More commendable uses of martureo and its derivatives in the New Testament fall loosely into three groups: simple evidence of a fact, or of a person’s reputation; verification of Jesus’ identity; and reports of his resurrection. Notable among the first group are: the requirement that two or three witnesses must agree in order for their testimony to be accepted (Mt.18:16, II Cor.13:1, Heb.10:28); Jesus’ instructions to people to give evidence of his having healed them (Mt.8:4, Lk.5:14, and Mk.1:44); and the integrity (or lack thereof) of individuals or groups (I Thess.2:10, Tit.1:13, Mk.6:11, and Lk.9:5). This idea may also figure in Jesus’ word to his followers regarding their own prospect of being hauled into court (Mk.13:9, Lk.21:13). Even with their lives on the line, they are told not to plan out their “testimony” in advance. By the Holy Spirit, he promises to guide it as needed.
Jesus frequently offered evidence for his claims regarding his relationship with the Father: Jn.5:31-37, 8:12-18, and 10:25, and 37-38. Everything he did was intended to serve as that evidence/ “witness”. This is reminiscent of the admonition attributed to Francis of Assisi, “Preach the Gospel at all times; use words only when necessary.” In Jn.15:26-27, both the promised Holy Spirit and the disciples themselves are entrusted with the same responsibility to give that evidence: “because you all are with me from the beginning.” (Are “lessons in witnessing” a substitute for having spent time with Jesus?) And Jesus himself reminded Nicodemus (Jn.3:11) that his own testimony dealt with what he knew and had experienced.
The overwhelming majority of NT references to “bearing witness” (for anyone other than Jesus himself) concern the glorious news of his Resurrection! This was the reason Peter gave for needing to choose as a replacement for Judas someone who (1) had been with Jesus, and (2)could testify that he is alive! (Ac.1:22). Clearly, this was the central burden of the New Testament sermons (Ac.2:24,32; 3:15, 5:32, 10:39,41; 13:31). It was the message that Festus found so confusing (Ac.25:19), and against which the ecclesiastical authorities campaigned so vigorously: “Jesus is alive!!!”
Still today, this is the source and the content of what we as his people have to offer to all who are still living in darkness, pain, or fear. Everything else—healings (Ac.3:11-15), changed lives (19-20), the consummated Kingdom (20-21) – is secondary to the fact that Jesus is alive and active among his people! As during his earthly ministry, it is his observable activity among us that serves as testimony (evidence) that the message is true! In the face of dire threats from the temple hierarchy, Peter and John (Ac.4:20) replied, “We cannot keep from speaking of what we have seen and heard!” Neither can we.
Faithful “witness” to our living Lord has nothing whatsoever to do with memorized “answers to questions that nobody is asking.” It has everything to do with our allowing him to create among us a fellowship (see Post #8) where his Life can be seen! Genuine “witness” is simply giving first-hand reports of that Life – when folks see it, and ask.
“You all ARE my witnesses!” (Lk.24:48).
The Pioneers' New Testament 
Good study, Mom. Taking your analogy a little further: in a courtroom, any evidence (and sometimes, even the suspicion) that a witness has been coached is sufficient to have his testimony stricken from the record, and can result in a contempt citation for either witness or coach.