From Johnson v. Louisville Ladder, 2008 U.S. Dist. LEXIS 102031 (S.D. Ala. Nov. 14, 2008):

In this case, Plaintiff has submitted the testimony of Dr. Dobbs in order to support his theory that a design defect caused the ladder's right foot to bend inward while he was standing on the ladder, causing him to fall. Defendants contend that certain portions of Dr. Dobbs' testimony are due to be stricken because they contradict his prior sworn deposition testimony. ***

Rule 56(e) of the Federal Rules of Civil Procedure requires that a party opposing a properly supported motion for summary judgment set forth specific facts, admissible as evidence, showing the existence of a genuine issue for trial. The rule specifically allows the court to consider the pleadings, depositions, answers to interrogatories and admissions on file, together with affidavits submitted by the opposing party in determining whether a genuine issue exists. However, "[w]hen a party has given clear answers to unambiguous questions which negate the existence of any genuine issue of material fact, that party cannot thereafter create such an issue with an affidavit that merely contradicts, without explanation, previously given clear testimony." Van T. Junkins & Associates, Inc. v. U.S. Indus., Inc., 736 F.2d 656, 657 (11th Cir. 1984). Accordingly, a district court may find an affidavit which contradicts testimony on deposition a sham when the party merely contradicts its prior testimony without giving any valid explanation. Id. at 656-658. In order to be stricken as a sham, an affidavit must be inherently inconsistent. See, e.g., Rollins v. TechSouth, Inc., 833 F.2d 1525 (11th Cir. 1987). Thus, a party cannot create a genuine issue of fact sufficient to survive summary judgment simply by filing an affidavit contradicting earlier deposition testimony. See, e.g., Tippens v. Celotex Corp., 805 F.2d 949, 954-955 (11th Cir. 1986). Such affidavits may be considered when the affidavit contains a satisfactory explanation of the contradictions between the affidavit and the affiant's earlier deposition testimony, or when newly discovered evidence furnishes a good faith basis for any inconsistency between the two. See, e.g., Clay v. Equifax, Inc., 762 F.2d 952 (11th Cir. 1985) (stating that when party has given clear answers to unambiguous deposition questions which negate the existence of a genuine issue of material fact, that party cannot thereafter create an issue of fact with an affidavit that merely contradicts the previous testimony).

... A close comparison of Dr. Dobbs' deposition testimony and his Affidavit reveals that it does not appear possible to harmonize the two. See, e.g., Fisher v. Ciba Specialty Chems. Corp., 238 F.R.D. 273, 284 (S.D. Ala. 2006). Rather, the comparison underscores the contradictory nature of the Affidavit, when compared to the prior deposition testimony, and supports a finding that certain portions of Dr. Dobbs' Affidavit are due to be disregarded and stricken under Junkins, 736 F.2d at 657. The Court notes as well, that Plaintiff has not asserted that the differences in Dr. Dobbs' more recent Affidavit are due to his attempt to explain or clarify an ambiguity in his prior deposition testimony. "If the Affidavit is intended as a mere clarification, then it is incumbent on the witness to explain the grounds for the clarification. This has not been done, and this Court will not indulge speculation as to the witness's thought processes in revising his opinions.[]" Fisher, 238 F.R.D. at 284 (footnote omitted).