1.  Hearsay

Affidavits are generally inadmissible hearsay and may not be introduced at trial for the truth of the matters assertd.{footnote}M’Iver v. Kyger, 16 U.S. 53, 4 L.Ed.2d 332 (___); Spivey v. United States, 912 F.2d 80 (4th Cir. 1990)(attorney’s affidavit); Roberts v. Harnischfeger Corp., 901 F.2d 42 (5th Cir. 1989); In re Knetzer, 243 F.2d 460 (7th Cir. 1957), cert. denied, Jaffke v. Dunham, 355 U.S. 835, 78 S.Ct. 55, 22 L.Ed.2d 46, rehg. denied, 355 U.S. 886, 78 S.Ct. 147, 2 L.Ed.2d 116; In re Burg, 103 B.R. 222 (9th Cir. BAP 1989).

Henry Cowell Lime & Cement Co. v. Industrial Accident Comm., 211 Cal. 154, 294 P. 703 (physician’s affidavit in worker’s compensation hearing); Brown v. Sheffield, 173 S.E.2d 891 (Ga. App. 1970) (but properly used for impeachment); In re Estate of Hartman, 65 Ill. App.3d 380, 381 N.E.2d 1221 (3d Dist. 1978), Friedman v. Sills, 112 App. Div. 2d 343, 491 NYS2d 794 (2d Dept. 1985); In re Eldridge, 82 N.Y. 161 (disbarrment hearing); Chapman v. Dickerson, 223 S.W. 318 (Tex. Civ. App.); Neal v. Commonwealth, 425 S.E.2d 521, 524 (Va. App. 1992) (search warrant .{/footnote}  For example, they are generally deemed hearsay where offered in favor of the affiant.{footnote}In re Brown, 82 F.3d 801 (8th Cir. 1996)(bankruptcy debtor’s affidavit offered in favor of debtor).{/footnote}  However they are often admitted to establish minesterial matters such as service of process,{footnote}Fed. R. Civ. P. 4(g).
Cal. C.C.P. § 2009 

Contra Queensboro Leasing, Inc. v. Resnick, 78 Misc. 2d 919, 358 NYS2d 939 (___).{/footnote} mailing,{footnote}R.A. Piloto, Inc. v. Allstate Ins. Co., 397 So.2d 1029 (3d Dist.)(affidavit of mail clerk).{/footnote} the loss of an original document for purposes of the best evidence rule,{footnote}Taylor v. Riggs, 26 U.S. 591, 7 L.Ed. 275 (__).{/footnote} or pursuant to special statutes or rules authorizing the use of affidavits.{footnote}E.g., United States Sentencing Guide § 6A1.3, comment (back’d);
Cal. Admin. Proc. Act, Cal. Govt. Code § 11514 (affidavits admissible in administrative proceedings subject to Act where opposing party given notice and oportunity to depose affiant; if no opportunity to depose, affidavit admissible but treated as hearsay); Cal. Evid. Code § 712 (in criminal trial as evidence of the technique used in taking blood samples); Vannier v. Superior Court, 32 Cal.3d 163, 185 Cal. Rptr. 427, 650 P.2d 302 (Uniform Act to Secure Attendance of Witnesses).{/footnote}  The most commonly invoked rules authorizing use of affidavits as evidence are those governing summary judgment.{footnote}Fed. R. Civ. P. 56(a). 
Check Friedman v. Sills, 112 App. Div. 2d 343, 491 NYS2d 794 (2d Dept. 1985).{/footnote}  They are often admitted in support of or in opposition to requests for an injunctive relief, but only after an answer to the complaint is on file.{footnote}Moss v. Balch, 320 Ill. App. 135, 49 N.E.2d 801 (___Dist. 1943).{/footnote}  Affidavits have also been held admissible under the residual exception to the hearsay rule.{footnote}F.T.C. v. Amy Travel Service, Inc., 875 F.2d 564, cert. denied, 110 S.Ct. 366, 107 L.Ed.2d 352 (1989).

But see Stokes v. City of Omaha, 23 F.3d 1362 (8th Cir. 1994)(affidavit of deputy police chief as to department’s discriminatory employment practices held not sufficiently trustworthy to be admissible under residual exception).{/footnote} 

An affidavit executed by an opposing party may be introduced as an admission.{footnote}National S.S. Co. v. Tugman, 143 U.S. 28, 36 L.Ed. 63, 12 S.Ct. 361; Chicago & N.R.Co. v. Ohle, 117 U.S 123, 29 L.Ed. 837, 6 S.Ct. 632.

Vartanian v. Croll, 117 Cal. App.2d 639, 256 P.2d 1022; Bageard v. COnsolidated Traction Co., 64 NJL 316, 45 A. 620. {/footnote}  Affidavits may also be used to impeach a testifying witness where the witness has executed an affidavit inconsistent with the witness’s testimony,{footnote}Colonial Refrigerated Transp., Inc. v. Mitchell, 403 F.2d 541 (5th Cir. 1968) (held erroneously excluded); NLRB v. Vangas, Inc., 517 F.2d 747 (9th Cir. 1975); Fuller v. Commissioner, 213 F.2d 102 (10th Cir. 1965).
Posner v. New York Life Ins. Co., 106 P.2d 488 (Ariz. 1940); Jackson v. Riviera Development Corp., 202 S.E.2d 545 (Ga. App. 1973); Brown v. Sheffield, 173 S.E.2d 891 (Ga. App. 1970); Owen v. Birmingham Federal Sav. & Loan Assoc., 183 N.W.2d 403 (Mich. App. 1970); Nathan v. McKernan, 101 N.W.2d 756 (Neb. 1960); In re Lesher’s Will, 269 App. Div. 812, 55 NYS2d 630; State v. Fales, 335 A.2d 920 (R.I. 1975); Cherb v. State, 472 S.W.2d 273 (Tex. Crim. 1971); Andrea G. Nadel, Annot., Admissibility Of Affidavit To Impeach Witness, 14 A.L.R.4th 828.
But see Hooks v. United States, 375 F.2d 212 (5th Cir. 1967) (prosecution not permitted to call witness it knows to be hostile for purpose of admitting affidavit as impeachment);
But see People v. Bugarin, 507 P2d 875 (Colo. 1973) (witness could not be impeached with another person’s affidavit); Sims v. State, 530 P.2d 1176 (Wyo. 1975) (no inconsistency where affidavit omitted detail provided in testimony).
CHECK Bethards v. Shivvers, Inc., 355 N.W.2d 39 (Iowa 1984) (unsigned affidavits admissible).{/footnote} but only after the witness has been afforded an opportunity to admit, deny, or explain them.{footnote}United States v. McCowan, (1972, CA10 Okla) 471 F2d 361 (10th Cir. 1972) (properly excluded)
Bill C. Harris Constr. Co. v. Powers, 554 S.W.2d 332 (Ark. 1977) (affidavit inadmissible where witness not provided opportunity to explain alleged inconsistency); Newton v. State, 272 So. 2d 15 (Fla. App. 1973), cert. denied, 278 So. 2d 627 and cert. denied, 414 U.S. 1157 (affidavit contradicting testimony from first trial inadmissible where witness no longer available and testimony is being used in retrial).
{/footnote}  Only those portions of the affidavit which are inconsistent may be introduced.{footnote}United States v. McCowan, 471 F.2d 361 (10th Cir. 1972).{/footnote}  See also IMPEACHMENT; INCONSISTENT STATEMENTS.

Failure to promptly object to an affidavit waives the issue of its admissibility.{footnote}Connecticut Mut. Life Ins. Co. v. Hillmon, 188 U.S. 208, 47 L.Ed. 446, 23 S.Ct. 294; Vartanian v. Croll, 117 Cal. App.2d 639, 256 P.2d 1022, Naficy v. Braker, 642 S.W.2d 282 (Tex. App. Houston (14th Dist.)).{/footnote}

2.  Personal Knowledge

An affidavit must be based on the personal knowlegde of the affiant.{footnote}Fed.R.Civ.P. 56(e) (summary judgment); Arkansas Best Freight System, Inc. v. Youngblood, 61 F.R.D. 565, 569 (W.D.  Ark. 1974).{/footnote}  Thus, affidavits made “on information an belief” are improper.{footnote}Judd v. Superior Court of Orange County, 60 Cal. App. 3d 38, 43, 131 Cal. Rptr. 246, 248 (1976){/footnote}  Even where the affidavit states that it is based on personal knowledge, it will be stricken if the contents reveal otherwise.{footnote}Shepley v. E. I. DuPont de Nemours and Company, Inc., 722 F. Supp. 506, 514 (C.D. Ill. 1989).{/footnote}