Witness Competency & Impeachment
Evidence · Lesson 07
Witness Competency & Impeachment
這一課問的是：證人是否有資格？得如何彈劾證人？
ActorActObjectStandardConsequence
Issue · what this lesson is really about
Is the witness competent — and how may the witness be impeached?
這一課問的是：證人是否有資格？得如何彈劾證人？
Trigger words & phrases that should flag this issue:
impeachprior convictionprior inconsistent statementbiascapacity
Core Terminology · 7 must-know
Tap a card to flip and reveal the meaning.
Rule 601
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Every person is competent to be a witness.
601 競爭力普遍。
Rule 602
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Personal knowledge required.
602 親身知識。
Rule 603
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Oath or affirmation required.
603 宣誓。
Rule 607
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Any party may impeach any witness.
607 任何方可彈劾任何證人。
Rule 608
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Character for truthfulness — reputation/opinion + cross-examination.
608 真實性人格。
Rule 609
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Prior criminal convictions for impeachment.
609 先前定罪。
Rule 613
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Prior inconsistent statements.
613 先前不一致陳述。
Rule Sentence · the workhorse
Under Rule 601, every person is competent to be a witness; Rule 607 permits any party to impeach any witness, including by prior inconsistent statements (Rule 613), prior convictions (Rule 609), bias, sensory defects, or character for untruthfulness (Rule 608).
Sentence Anatomy · 5 roles, 5 colors
Every rule sentence breaks into five visual roles.
Actor 行為人examining party詰問之當事人
Act 行為impeaching witness彈劾證人
Object 對象witness credibility證人可信度
Standard 法律標準Rules 601-613Rules 601-613
Consequence 後果credibility attacked可信度受挑戰
Casebook Snapshot · a real American case
Luce v. United States
Holding. To preserve for appeal a challenge to a Rule 609 ruling admitting prior convictions for impeachment, the defendant must actually testify; an in-limine ruling on impeachment is not appealable if the defendant declines to testify.
Why it matters. Luce forces strategic commitment: claim 609 error only if you actually take the stand.
Luce：609 駁回之保留須實際作證方可上訴。
Common Mistakes · what trips students
✗ party 不能彈劾自家證人。
✓ Rule 607: any party may impeach any witness.
Rule 607：任何方可彈劾任何證人。
✗ 所有定罪都可採。
✓ Subject to 609 balancing and 10-year limit.
須 609 衡平與 10 年限。
Mini IRAC · build the Application
Issue. May the prosecution use D's prior felony conviction for grand larceny (a crime of dishonesty) to impeach D when D testifies?
Rule. Under Rule 609(a)(2), any witness — including criminal defendants — may be impeached with prior convictions for crimes involving dishonesty or false statements without Rule 403 balancing.
Application (model). D testifies in his own defense; the prosecution seeks to impeach with a prior grand larceny conviction. Because Rule 609(a)(2) admits crimes of dishonesty for impeachment without Rule 403 balancing — and larceny is treated as such — the fact that D's prior conviction was for grand larceny (an offense involving dishonesty) means impeachment is automatic.
Pick the right element for each blank:
g1.
g2.
g3.
Conclusion. Therefore, the prosecution may use the prior conviction to impeach.
MBE Check · multiple choice
W testifies for D. On cross, P seeks to ask about a 7-year-old felony conviction for tax fraud. May the prosecution impeach?
Practice Drill · tap to build the rule
Drop the chips here in correct order:
Tap chips to add → tap chips in the target to remove: