What is Infamy?

Legal Definition
Infamy, in common usage, is the notoriety gained from a negative incident or reputation (as opposed to fame). The word stems from the Latin infamia, antonym of fama (in the sense of "good reputation").
-- Wikipedia
Legal Definition
Crim. law, evidence. That state which is produced by the conviction of crime and the loss of honor, which renders the infamous person incompetent as a witness.

2. It is to be considered, 1st. What crimes or punishment incapacitate a witness. 2d. How the guilt is to be proved. 3d. How the objection answered. 4th. The effect of infamy.

3. - 1. When a man is convicted of an offence which is inconsistent with the common principles of honesty and humanity, the law considers his oath to be of no weight, and excludes his testimony as of too doubtful and suspicious a nature to be admitted in a court of justice to deprive another of life, liberty or property. Gilb. L. E. 256; 2 Bulst. 154; 1 Phil. 23; Bull. N. P. 291. The crimes which render a person incompetent, are treason; 5 Mod. 16, 74; felony; 2 Bulst. 154; Co. Litt. 6; T. Raym. 369; all offences founded in fraud, and which come within the general. notion of the crimen falsi of the Roman law; Leach, 496; as perjury and forgery; Co. Litt. 6; Fort. 209; piracy 2 Roll. Ab. 886; swindling, cheating; Fort. 209; barratry; 2 Salk. 690; and the bribing a witness to absent himself from a trial, in order to get rid of his evidence. Fort. 208. It is the crime and not the punisshment which renders the offender unworthy of belief. 1 Phill. Ev. 25.

4. - 2. In order to incapacitate the party, the judgment must be proved as pronounced by a court possessing competent jurisdiction. 1 Sid. 51; 2 Stark. C. 183; Stark. Ev. part 2, p. 144, note 1; Id. part 4, p. 716. But it has been held that a conviction of an infamous crime in another country, or another of the United States, does not render the witness incompetent on the ground of infamy. 17 Mass. 515. Though this doctrine appears to be at variance with the opinions entertained by foreign jurists, who maintain that the state or condition of a person in the place of his domicil accompanies him everywhere. Story, Confl. 620, and the authorities there cited; Foelix, Trait« De Droit Intern. Priv«, 31; Merl. R«pert, mot Loi, 6, n. 6.

5. - 3. The objection to competency may be answered, 1st. By proof of pardon. See Pardon. And, 2d. By proof of a reversal by writ of error, which must be proved by the production of the record.

6. - 4. The judgment for an infamous crime, even for perjury, does not preclude the party from making an affidavit with a view to his own defence. 2 Salk. 461 2 Str. 1148; Martin's Rep. 45. He may, for instance, make an affidavit in relation to the irregularity of a judgment in a cause in which he, is a party, for otherwise he would be without a remedy. But the rule is confined to defence, and he cannot be heard upon oath as complainant. 2 Salk. 461 2 Str. 1148. When the witness becomes incompetent from infamy of character, the effect is the same as if he were dead and if he has attested any instrument as a witness, previous to his conviction, evidence may be given of his handwriting. 2 Str. 833; Stark. Ev. part. 2, sect. 193; Id. part 4, p. 723.

7. By infamy is also understood the expressed opinion of men generally as to the vices of another. Wolff, Dr. de la Nat. et des Gens, 148.
-- Bouviers Law Dictionary
Legal Definition
A qualification of a man's legal status produced by his conviction of an infamous crime and the consequent loss of honor and credit, which, at common law, rendered him incompetent as a witness, and by statute in some jurisdictions entails other disabilities. McCafferty v. Guyer, 59 Pa. 116; Ex parte Wilson, 114 U. S. 417, 5 Sup Ct. 935, 29 In Ed. 89; State v. Clark, 60 Kan. 450, 56 Pac. 767.
-- Black's Law Dictionary
Legal Definition
Infamia in facti, which see; infamia juris, which disqualifies one as a witness. See 114 U. S. 417, 29 L, Ed. 89, 5 Sup. Ct. Rep. 935.
-- Ballentine's Law Dictionary