13.2 Witness Evaluation, Preparation, Obstruction of Justice & Witness Tampering
Key Takeaways
- Evaluate witnesses on stated factors — personal knowledge under Evidence Code § 702, capacity under Evidence Code § 701, bias and interest, prior consistency, corroboration, and impeachability under Evidence Code § 780 — not on instinct.
- Preparing a witness means familiarising them with the process and their own prior statements; it never means suggesting content, and the line is the difference between advocacy support and Penal Code § 137 subornation.
- Penal Code § 136.1 makes it a crime knowingly and maliciously to prevent or dissuade a witness or victim from attending or giving testimony, and it is a felony when accompanied by force or threat under § 136.1(c).
- Penal Code § 137 reaches inducing false testimony — offering a bribe is a felony under § 137(a), and knowingly inducing false statements is punishable under § 137(b)–(c).
- Paying a fact witness for their testimony is improper; reimbursing reasonable expenses and statutory witness fees under CCP § 1986.5 and Government Code § 68093 is not.
Witness Evaluation, Preparation, Obstruction of Justice & Witness Tampering
Core Practice Standard: Task T26 asks the investigator to assess witnesses for strengths and weaknesses, which is a different exercise from taking a statement. Counsel needs to know, before committing to a witness, whether that person will hold up. The associated knowledge statements pair that skill with its criminal boundary: the laws on obstruction of justice, witness intimidation, and tampering. The two belong together because the same conversation, conducted two different ways, is either professional preparation or a felony.
1. Structured Witness Evaluation
Threshold Competency
Evidence Code § 701 disqualifies a person as a witness only if they are incapable of expressing themselves so as to be understood, or incapable of understanding the duty to tell the truth. Evidence Code § 702 requires personal knowledge of the matter — the witness must have perceived it. Those are low bars, and the real work is the assessment that follows.
The Assessment Matrix
| Factor | The question | Where it bites |
|---|---|---|
| Perception | Where were they, what was the distance, lighting, obstruction, duration? | Cross-examination on capacity to observe |
| Memory | How long ago; did they record anything contemporaneously? | Evidence Code § 780(c) capacity to recollect |
| Consistency | Do the statements over time match, and match the documents? | Prior inconsistent statement, Evidence Code § 1235 |
| Bias and interest | Employment, family, financial stake, litigation history | Evidence Code § 780(f) bias, interest, or other motive |
| Character for honesty | Prior conduct or convictions admissible for impeachment | Evidence Code §§ 780(e), 788 |
| Communication | Can they answer the question asked, without volunteering? | Practical credibility with a jury |
| Availability | Within subpoena range, likely to appear, health, immigration concerns | Evidence Code § 240 unavailability; the need to preserve testimony |
| Corroboration | Is anything they say independently verifiable? | Weight |
Report each factor honestly to counsel, including the damaging ones. A witness assessment that omits the fact that the witness is the plaintiff's cousin is worse than no assessment, because counsel will build on it.
Preserving Testimony at Risk
Where availability is uncertain — a witness who is elderly, seriously ill, or about to leave the jurisdiction — the answer is not a better statement. It is to tell counsel early enough that a deposition can be taken. A recorded statement is hearsay; a deposition taken with notice and cross-examination can be admitted under Evidence Code § 1291 if the witness later becomes unavailable under Evidence Code § 240. That timing recommendation is one of the most valuable things an investigator contributes to a case.
2. Lawful Witness Preparation (K95)
+---------------------------------------------------------------------------+
| PERMITTED | PROHIBITED |
+-------------------------------------+-------------------------------------+
| Explain the process, the room, | Suggest what the answer should be |
| the roles, and what to expect | |
| Review the witness's own prior | Supply facts the witness does not |
| statements and documents | independently remember |
| Explain: answer only what is | Script the wording of answers |
| asked; say "I don't know" if true | |
| Identify likely cross-examination | Coach the witness to avoid a topic |
| areas so they are not ambushed | or to feign lack of memory |
| Reimburse reasonable expenses and | Pay for testimony or condition pay |
| tender statutory witness fees | on its content |
+-------------------------------------+-------------------------------------+
The organising principle: prepare the witness, not the testimony. Reviewing a witness's own prior statement so they are not surprised by it is proper. Telling them what a different witness said, so their account converges, is not.
Fees. A witness may be reimbursed for reasonable travel and lost earnings, and statutory witness fees are tendered under Code of Civil Procedure § 1986.5 and Government Code § 68093. Paying a fact witness for their testimony, or contingent on its content or the case outcome, is improper and, depending on the facts, a bribe under Penal Code § 137(a). Expert witnesses are properly compensated for their time — that distinction between fact and expert witnesses is a common examination item.
3. The Criminal Boundary
| Statute | Conduct | Notes |
|---|---|---|
| Penal Code § 136.1(a)–(b) | Knowingly and maliciously preventing or dissuading, or attempting to prevent or dissuade, a witness or victim from attending or giving testimony, or from reporting a crime | A "wobbler" — chargeable as a misdemeanour or felony |
| Penal Code § 136.1(c) | The same conduct accompanied by force or an express or implied threat of force or violence, or for pecuniary gain, or as part of a conspiracy | Felony |
| Penal Code § 137(a) | Giving or offering a bribe to influence testimony | Felony |
| Penal Code § 137(b) | Knowingly inducing a false statement by force or threat | Offence |
| Penal Code § 137(c) | Knowingly inducing a person to give false material information pertaining to a crime to a law enforcement official | Misdemeanour |
| Penal Code § 138 | Bribery of a witness to be absent, and the witness receiving it | Offence |
| Penal Code § 127 | Subornation of perjury — procuring another to commit perjury | Felony |
| Penal Code § 148(a)(1) | Wilfully resisting, delaying, or obstructing a peace officer or emergency medical technician in the discharge of duty | Misdemeanour; a conviction is an express disciplinary ground under BPC § 7561.1(k) |
| Penal Code § 32 | Accessory after the fact — harbouring or concealing a principal to avoid arrest or trial | Offence |
Two points investigators most often get wrong:
- Telling a witness they do not have to speak with the other side is lawful. A witness belongs to neither party, and either party may accurately tell them they are free to decline an interview. Telling them to avoid service, leave the jurisdiction, or not appear under subpoena crosses into § 136.1. The distinction is between accurately describing a right and dissuading attendance or testimony.
- Implied pressure counts. § 136.1(c) reaches an implied threat of force or violence. A remark about knowing where someone works, delivered in a tone the witness reasonably reads as a threat, is not saved by the absence of an explicit threat.
Represented parties. Where an attorney directs the work, California Rule of Professional Conduct 4.2 bars communicating about the subject of the representation with a person the lawyer knows to be represented, and Rules 5.3 and 8.4(a) extend responsibility to the lawyer's non-lawyer agents. An investigator who interviews a represented adverse party can produce disqualification of counsel and suppression of the statement.
Case Example: Two Conversations
Scenario A. An investigator meets a defence witness, reviews her signed statement with her, explains the courtroom layout, tells her to answer only the question asked and to say she does not remember if she does not, and warns her that opposing counsel will probe the fact that she was 40 metres away in poor light.
Scenario B. The same investigator meets a second witness, tells him what the first witness said so their accounts "line up," mentions that the defendant's family would be grateful and that there might be "something for his trouble" after the trial, and adds that the witness "wouldn't want the hassle" of being served.
Analysis. Scenario A is textbook lawful preparation: process familiarisation, review of the witness's own prior statement, general instructions on how to testify, and honest identification of a cross-examination weakness. Nothing supplies content.
Scenario B is three separate offences. Supplying another witness's account to align testimony is inducing a false statement and, if the resulting testimony is false, subornation of perjury under Penal Code § 127. Offering "something for his trouble" is a bribe to influence testimony under Penal Code § 137(a), a felony. And the remark about the "hassle" of being served is an attempt to dissuade a witness from attending, within Penal Code § 136.1, aggravated to a felony under § 136.1(c) if the witness reasonably reads it as an implied threat. Any one of them ends the licence under BPC § 7561.1 and the fraud and dishonesty grounds in BPC § 7538(a)(2).
Which witness-preparation activity crosses from lawful preparation into criminal conduct?
An investigator tells a reluctant witness, 'You don't have to talk to the other side's lawyer if you don't want to.' Then adds, 'And you probably wouldn't want the hassle of being served — maybe stay with your sister for a few weeks.' How does California law treat these two statements?
A fact witness asks to be paid for the two days of work she will miss to testify. What may the investigator lawfully offer?
Counsel asks an investigator to assess whether a witness should be called. Which combination of authorities frames the assessment?