As a general rule, if those who serve on the jury are as well qualified by knowledge or experience as the witness to understand the evidence or to derive the proper inferences from the facts, expert testimony is not admissible.55 This is because, in such circumstances, the jury may be trusted to form an opinion as intelligent and reliable as that of the witness and there is no need for the admission of such testimony. However, even when the jurors are well equipped to make judgments on the basis of their common knowledge or experience, a court may admit expert testimony if it concludes that the specialized knowledge the expert brings to bear on the issue may be helpful to the trier of fact.56

There are certain areas reserved exclusively for the trier of fact which may be out of bounds for any witnesses, whether or not expert. Thus, a witness, whether or not an expert, may not testify that a party was negligent. The negligence standard is that of a reasonable   person, which is to be determined by the representatives of a cross section of the community (or, if trial by jury is waived, by a judge).57 It is unlikely that a Delaware court, despite the elimination of the restriction on experts testifying as to the ultimate issue,58 would allow witnesses to express their opinions on this subject. An exception to this is in medical malpractice cases where expert testimony is required by statute to establish the applicable standard of care and whether the facts justify a finding that it has been violated.59

In personal injury actions, if the alleged negligent conduct is specifically authorized or permitted by the applicable statutes, codes, or regulations, then an expert is necessary in order to establish that the standard of care in the relevant community is higher than the standard of care created by such regulations. However, if the applicable regulations neither address nor permit the alleged negligent conduct, such an expert is not required because it is unnecessary for the plaintiff to prove that the local standard of care is greater than the base-line minimal standard created by the codes.60 

Expert testimony as to the condition of property, such as a sidewalk, that is claimed to have caused injury is not properly admissible, as the jury can observe the condition of property, either directly or through photographs, or hear testimony about the condition of the property, and is equally able to determine whether the property was or was not in good repair.61 However, expert testimony is required to establish the effect of construction or nearby trees and shrubbery.62

Experts may not opine concerning applicable domestic law, as that is exclusively within the province of the court.63 Although an expert may not testify as to a legal conclusion, an expert may testify as to the subject matter which precedes a legal conclusion. In other words, an examiner may explore with the expert the legal criteria for forming such an opinion.64 Similarly, it is improper for an expert to testify as to the appropriate amount of punitive damages, as that is within the province of the trier of fact.65 It is proper to have an expert define uncommon terms according to the customs and usages of the trade or business with which the expert is familiar.66 The value of damaged goods is also within the exclusive knowledge of expert witnesses.67 A state trooper with experience in investigating accidents and driving in adverse road conditions has been deemed qualified to opine on the maximum safe speed in a given area at a given time, where the trooper had observed the area and its conditions at the time.68  Similarly, courts have consistently permitted police officers, trained and experienced in accident investigation, to qualify as experts and to give opinion testimony as to the point of impact in an automobile collision based on physical evidence observed at the accident site.69

Expert testimony that a party does or does not fit a particular profile, such as the profile of a pedophile, is not admissible, as such testimony amounts to opinion about a party’s character traits for the purpose of showing that the party acted in conformity therewith, which violates Delaware Rule of Evidence 405.70

Typically, though not in all cases, expert testimony is required to prove causation in actions for breach of an implied warranty of merchantability.71 While most product defect cases require expert testimony, there is a narrow category of cases where, if circumstantial evidence tends to negate other reasonable causes of the injury such that a prima facie case is established, expert evidence is not required.72

Opinion testimony is not permitted on aspects of human nature that are deemed to be matters of common knowledge or experience, such as the fact that, when walking, people tend to cut corners.73

55. Wheat v. State, 527 A.2d 269, 272 (Del. 1987); Seiler v. Levitz Furniture Co. of Eastern Region, Inc., 367 A.2d 999, 1008 (Del. 1976); Wagner v. Shanks, 194 A.2d 701, 706 (Del. 1963); Robelen Piano Co. v. Di Fonzo, 169 A.2d 240, 246 (Del. 1961); South Atlantic S.S. Co. v. Munkacsy, 187 A. 600, 605 (Del. 1936), cert. denied, 299 U.S. 607 (1936); Scotton v. Wright, 122 A. 541, 544 (Del. Ch. 1923); Ramada Inns v. Dow Jones & Co., C.A. No. 83C-AV-56, slip op. at 9-10, Poppiti, J. (Del. Super. Mar. 10, 1988). See also Hearn v. Wilmington City R. Co., 76 A. 629 (Del. Super. 1910) (expert testimony as to effect of fog on light is not admissible, it being a matter which persons of ordinary experience and intelligence are competent to judge).

56. Ramada Inns v. Dow Jones & Co., C.A. No. 83C-AV-56, slip op. at 10, Poppiti, J.  (Del. Super. Mar. 10, 1988).

57. See Robelen Piano Co. v. Di Fonzo, 169 A.2d 240, 245 (Del. 1961).

58. D.R.E. 704.

59. 18 Del. C. § 6853.

60. Small v. Super Fresh Food Markets, Inc., C.A. No. 07C-12-095 RRC, slip op. at 2, Cooch, J. (Del. Super. Feb. 12, 2010); Vandiest v. Santiago, C.A. No, 02C-06-003 WLW, slip op. at 18-19, Witham, J. (Del. Super. Dec. 9, 2004). See also Rossman v. Lincoln Property Co., Inc., C.A. No. 06C-09-169 (SCD), Del Pesco, J. (Del. Super. Mar. 5, 2008) (“[t]he liability theories here, related to leaf removal and adequacy of illumination, are not so clearly outside the scope of ordinary experience as to make expert testimony essential”).

61. Freiman v. Evans, C.A. No. 94C-02-231-JOH, slip op. at 3, Herlihy, J. (Del. Super. Aug. 9, 1997).

62. Carey v. Guy A. DiSabatino & Associates, C.A. No. 2007-12-164, Welch, J. (Del. Comm. Pls. June 5, 2009).

63. Itek Corp. v. Chicago Aerial Industries, Inc., 274 A.2d 141, 143 (Del. 1971).

64.  North America Philips Corp. v. Aetna Cas. & Sur. Co., C.A. No. 88C-JA-155, slip op. at 7-9, Bifferato, J. (Del. Super. Apr. 22, 1995).

65. Farrall v. A.C. & S. Co., 558 A.2d 1078, 1081-83 (Del. Super. 1989).

66. Itek Corp. v. Chicago Aerial Industries, Inc., 274 A.2d 141, 143 (Del. 1971).

67. Storey v. Castner, 314 A.2d 187, 192 (Del. 1973); Stuart v. Rizzo, 242 A.2d 477, 480 (Del. 1968).

68. Yankanwich v. Wharton, 460 A.2d 1326, 1329-30 (Del. 1983).

69. Szewczyk v. Doubet, 354 A.2d 426, 428 (Del. 1976).

70. State v. Floray, 715 A.2d 855 (Del. Super. 1997), aff’d, 720 A.2d 1132 (Del. 1998).

71.  Reybold Group, Inc. v. Chemprobe Technologies, Inc., 721 A.2d 1267, 1270 (Del. 1998).

72. Reybold Group, Inc. v. Chemprobe Technologies, Inc., 721 A.2d 1267, 1267 (Del. 1998); Brown v. Dollar Tree Stores, Inc., C.A. No. 07C-07-092 RRC, slip op. at 9-10, Cooch, J. (Del. Super. Dec. 9, 2009).

73. Ward v. Shoney’s, Inc., 817 A.2d 799, 803 (Del. 2003).

© 2010  David L. Finger