Appellants Sears and General Electric contend that the lower court erred in this products liability action by denying their motions for judgment n.o.v. or for a new trial on grounds that the verdict was against the weight of the evidence. Appellant General Electric also contends the lower court erred in evidentiary rulings, in instructing the *449jury, and in requiring it to indemnify Sears. We find these contentions without merit and, accordingly, affirm.
In reviewing a denial of judgment n.o.v: we must view the evidence in the light most favorable to the verdict winner and draw all reasonable inferences and resolve all conflicts in testimony in that party’s favor. Schneider v. Albert Einstein Medical Center, 257 Pa.Superior Ct. 348, 390 A.2d 1271 (1978). In reviewing a denial of a motion for a new trial we must consider all the evidence. Only when the jury’s verdict is so contrary to the evidence as to shock one’s sense of justice should a new trial be granted. A lower court’s decision in this regard will not be reversed absent an abuse of discretion. Yandrich v. Radic, 291 Pa.Superior Ct. 75, 435 A.2d 226 (1981). So viewed, the facts are as follows:
On August 8, 1970, appellee Paul Burch was cutting grass with an electric lawn mower. Twice the mower shut off and would not restart until he pushed the reset button. About the third time the motor shut off, he decided to unclog the rotor blade. He placed the mower on its side without disturbing the reset button, then reached in to remove clumps of grass with his left hand. The motor restarted, severely injuring his hand. His index and middle fingers were subsequently amputated, his ring finger permanently immobilized, and his thumb and little finger shortened.
On July 25, 1972, appellee sued Sears, which had originally sold the mower under its “Craftsman” brand name. Appellee alleged the lack of “deadman’s switch,” that would have automatically turned off the power when the operator released the controls, was a defect in the mower’s design. On August 17, 1973, Sears sued General Electric, the supplier of the mower’s electrical system including the reset button, motor, and on/off switch. General Electric in turn sued Texas Instruments, the manufacturer of the reset button and its thermal cut-off switch. After trial on February 7, 1979, the jury awarded appellee $20,000 plus interest against Sears. It found for Sears against General Electric *450and exonerated Texas Instruments. The lower court, on September 2, 1980, entered judgment in favor of Burch and requiring equal contribution between Sears and General Electric. However, on September 30, it modified that judgment to require General Electric to wholly indemnify Sears. Post-trial motions were denied, and Sears and General Electric have appealed.
Appellants raise three sets of contentions concerning judgment n.o.v. and the weight of the evidence: (1) that appellee did not prove the lack of a deadman’s switch was a “defect”; (2) that appellee’s placing his hand near the blade was either extraordinary consumer behavior negating defect, a superseding cause, or an assumption of the risk; and (3) that the mower was substantially changed since leaving the seller.
Several courts have held that the lack of a dead-man’s switch, that would automatically turn-off machinery when a user relaxes his grip on the controls, presents a jury question of a lawn mower’s defective design. See Baker v. Outboard Marine Corp., 595 F.2d 176 (3d Cir.1979) (applying Pennsylvania law); Daniels v. McDonough Power Equipment Inc., 430 F.Supp. 1203 (D.Miss.1977); Schurr v. Royal Globe Ins. Co., 353 So.2d 215 (Fla.App.1977); Hubbard v. McDonough Power Equipment, Inc., 83 Ill.App.3d 272, 38 Ill.Dec. 887, 404 N.E.2d 311 (1980). See generally Annot., 41 A.L.R.3d 986 (1972 & Supp.1982). A manufacturer or seller is strictly liable if a defect in its product causes injuries to a user. Webb v. Zern, 422 Pa. 424, 220 A.2d 853 (1966); Restatement (Second) of Torts § 402A. A product is defective if it is unsafe for its intended use. Azzarello v. Black Bros. Co., 480 Pa. 547, 391 A.2d 1020 (1978). The finding of a defect requires a balancing of the utility of the product against the seriousness and likelihood of the injury and the availability of precautions that, though not foolproof, might prevent the injury. Schell v. AMF, Inc., 567 F.2d 1259 (3d Cir.1977). When submitting the issue of defect to a jury, the court must first view the evidence in the light most favorable to the plaintiff to *451determine if a defect may be found. Azzarello v. Black Bros. Co., supra.1 Here, appellee’s expert testified the mower was unsafe because it lacked a deadman’s switch, such as is used on electric saws and drills, that would have turned-off the mower’s electric current when the operator relaxed his grip. The expert testified that such switches, costing less than five dollars, were available at the time of design and could prevent inadvertent restarting and the attendant risks of injury. Appellants’ expert countered with testimony that a deadman’s switch had been considered, tested, and rejected during the design of this mower. He asserted that the deadman’s switch would interfere with an operator’s keeping the cord clear of the blade, would be less durable and therefore less reliable than the existing on/off switch, and finally might have its safety advantages negated by a consumer tendency to tie it in the “on” position. Viewing this evidence in the light most favorable to the verdict, we are satisfied that the jury could reasonably conclude that failing to provide the extra safety margin afforded by the deadman’s switch rendered the product unsafe. Thus, judgment n.o.v. was properly denied. Upon considering all the evidence, it is neither patently unreasonable nor shocking to the conscience that the jury would give greater weight to appellee’s expert testimony. Thus, the lower court’s denial of a new trial on this point was not an abuse of discretion.
Appellants contend next that appellee’s reaching his hand into the stalled mower constituted either a voluntary assumption of the risk or such extraordinary consumer behavior as to negate the defect or its causal connection to the accident. Because a product is defective only if it is unsafe for its intended use, Azzarello v. Black Bros. Co., supra, a finding of defect may be precluded when the *452plaintiff is injured when using the product in an “abnormal” manner. Bartkewich v. Billinger, 432 Pa. 351, 247 A.2d 603 (1968). An allegedly abnormal use will negate liability, however, only if it was not reasonably foreseeable by the seller. Id.; Eshbach v. W.T. Grants & Co., 481 F.2d 940 (3d Cir.1973). For instance, a plaintiffs placing his hand into the operating machinery of a glass crusher was held so abnormal and unforeseeable as to preclude a finding of defect as a matter of law. Bartkewich v. Billinger, supra. See Leach v. Jagenberg-Werke A.G., 480 F.Supp. 244 (E.D. Pa.1979). However, that a user might place a hand near apparently stopped machinery or parts has been held to be sufficiently foreseeable to sellers to raise a jury question as to defect for failure to provide adequate safeguards. E.g., Schell v. AMF, Inc., supra; Elder v. Crawley Book Machinery Co., 441 F.2d 771 (3d Cir.1971); Taylor v. Paul O. Abbe, Inc., 380 F.Supp. 601 (E.D.Pa.1974); Dorsey v. Yoder Co., 331 F.Supp. 753 (E.D.Pa.1971), aff'd mem. 474 F.2d 1339 (3d Cir.1973). The related issue of causation is raised when the plaintiffs action is so reckless that the plaintiff would have been injured despite the curing of any alleged defect, or is so extraordinary and unforeseeable as to constitute a superseding cause. Bartkewich v. Billinger, supra; Sherk v. Daisy-Heddon Corp., 498 Pa. 594, 450 A.2d 615 (1982) (firing gun at victim’s head); Dorsey v. Yoder, supra. Finally, because assumption of risk may be a defense to a strict liability claim, Ferraro v. Ford Motor Co., 423 Pa. 324, 223 A.2d 746 (1966), when the plaintiff places himself in a position of danger, while consciously aware of and appreciating the danger, and not as a result of momentary inattention or inadvertence, he may be found to have assumed the risk, thus precluding liability. E.g., Schell v. AMF, Inc., supra; Green v. Parisi, 478 F.2d 313 (3d Cir.1973). But if the plaintiff believed his hand to be in a safe position, the jury may conclude that he has not in fact assumed the risk. Id.; Greco v. Bucciconi, 407 F.2d 87 (3d Cir.1969). Here, appellee testified that the motor was completely stopped and silent as it had been on the two prior stall-outs when it would not start until he pushed the *453reset button. His expert testified that the extra level of safety afforded by a deadman’s switch could have prevented the motor from accidently restarting regardless of what had stopped the motor. Upon resolving doubts and conflicts in testimony, we find the jury could reasonably conclude that appellants could foresee that the motor might stall and that a user might attempt to unclog the blade by placing some part of his body near the blade. Thus, the conduct does not require a new trial or judgment n.o.v. on the issues of abnormal use or superseding cause. Similarly, the jury could reasonably conclude from the record that appellee believed the motor to be stopped so that it could not be restarted except by the reset button mechanism and therefore did not voluntarily assume the risk. Thus, the lower court did not abuse its discretion by denying the motions for judgment n.o.v. or new trial on these points.
Appellants’ third contention is that the mower had been substantially changed in the seven years between its manufacture and the accident. If the condition of a product is “substantially changed” before it reaches the consumer, the manufacturer or seller will not be held strictly liable. Berkebile v. Brantly Helicopter Corp., 462 Pa. 83, 337 A.2d 893 (1975); Restatement (Second) of Torts § 402A (e.g. raw material to finished goods). Also, if a product originally reaches the consumer as manufactured, and the plaintiff alleges a defect due to a malfunction, such as failing brakes, secondary causes, such as wear, tear, and deterioration may be found to have negated the causal link between the original condition of the product and the accident. Kuisis v. Baldwin-Lima-Hamilton Corp., 457 Pa. 321, 319 A.2d 914 (1974). Here, however, appellee asserts not an unexplained malfunction but a specific design defect—the lack of a deadman’s switch as a safeguard against inadvertent restarting. None of the changes argued by appellants affected that design. Appellants showed that the mower had a replacement electrical cord, pitting and arcing on its plug, was purchased used, and had suffered wear and tear. Appellee rebutted the seriousness of the *454pitting and arcing and the condition of the replacement cord. In resolving the conflicting testimony, the jury could reasonably have found that the cord and plug were not the cause of the stopping and restarting. Moreover, regardless of why the motor stalled, the jury had a basis to conclude that such stalling was foreseeable to the sellers and that the unchanged design lacking a deadman’s switch failed to protect against uncontrolled restarting. Accordingly, the lower court properly denied judgment n.o.v. and new trial.
General Electric contends next that appellee’s expert witness was not qualified to testify as an expert and that he lacked a factual basis on which to give competent testimony on the defectiveness of the design. The qualification of an expert witness is a matter within the discretion of the trial court. Kravinsky v. Glover, 263 Pa.Superior Ct. 8, 396 A.2d 1349 (1979). If the witness has “sufficient skill, knowledge, or experience in [the] field or calling as to make it appear that his opinion or inference will probably aid the trier in his search for truth,” McCormick on Evidence, supra at 30 (footnote omitted), he or she is qualified as an expert. Once the expert shows he has some basis in fact for his opinion, his testimony is admissible. Id. Appellee’s expert had a Ph.D. in mechanical engineering from the University of Pennsylvania. He did consulting work on the design of machinery, including safety devices, for Scott Paper Company and taught engineering at several universities. Even though he had never specifically designed lawnmowers, he nonetheless had a reasonable pretension to relevant specialized knowledge. He examined and tested this mower and its components after the accident. Although he never obtained or tested a similar mower with a deadman’s switch and several years had elapsed between the accident and his tests, the lower court acted within its discretion in determining he did indeed have a basis in fact for his opinion on the design of the mower.
General Electric contends also that it should be granted a new trial because the lower court excluded photographs of the mower with which it sought to cross-examine *455appellee’s expert. Questions of the admission and exclusion of evidence are within the sound discretion of the trial court and will not be reversed on appeal absent an abuse of discretion. Lewis v. Mellor, 259 Pa.Superior Ct. 509, 393 A.2d 941 (1978). The court may exclude evidence that is irrelevant or merely cumulative of other evidence. Id. Here, the excluded photograph showed tape on the mower’s electrical cord three years after the accident. General Electric’s cross-examination placed the fact of the tape before the jury, but not the photograph. After objection, counsel withdrew his hypothetical question about the significance of the tape to the stalling and restarting. Moreover, appellee’s theory of a design defect affording insufficient protection against restarting did not depend heavily on the exact cause of the mower’s stopping. Consequently, the lower court acted within its discretion in excluding the photograph.
General Electric contends next that the lower court erred when charging the jury on defect and assumption of risk. A trial judge has wide latitude in charging the jury, and may use any particular language provided he adequately and fully conveys to the jury the law applicable to the facts of the case. Albert v. Alter, 252 Pa.Superior Ct. 203, 381 A.2d 459 (1977); Churchill v. Eakin, 233 Pa.Superior Ct. 466, 335 A.2d 378 (1975). Contrary to appellant’s allegations that the charge in effect mandated the jury to find a defect and misled it concerning the understanding of the danger needed for an assumption of the risk, we find the charge adequately and fairly presented the question to the jury. See Azzarello v. Black Bros. Co., supra (defect); Jones v. Three Rivers Management Corp., 483 Pa. 75, 394 A.2d 546 (1978) (assumption of risk).
General Electric contends that the lower court erred in requiring it to indemnify Sears. Specifically, it alleges the jury’s verdict did not support the court’s judgment wholly shifting liability. Alternatively, it contends that if the verdict did not have that effect, it was against the weight of the evidence. We find these contentions without *456merit. Under our products liability law, all suppliers of a defective product in the chain of distribution, whether retailers, partmakers, assemblers, owners, sellers, lessors, or any other relevant category, are potentially liable to the ultimate user injured by the defect. Francioni v. Gibsonia Truck Corp., 472 Pa. 362, 372 A.2d 736 (1977); Grubb v. Albert Einstein Medical Center, 255 Pa. Superior Ct. 381, 387 A.2d 480 (1978); Kitzinger v. Gimbel Bros., Inc., 240 Pa.Superior Ct. 345, 368 A.2d 333 (1976). This rule of law ensures the availability of compensation to the injured party, and helps place the burden of such injury on parties who, unlike the consumer, have a better opportunity to control the defect or spread its costs through pricing. See Berkebile v. Brantly Helicopter Corp., supra; Webb v. Zern, supra. To further achieve these policies and to do justice among the potential defendants, Pennsylvania permits the remedies of indemnity and contribution2 so that as among those in the chain of distribution liability may ultimately rest with, or be shared equally among, those who can best detect, control, or prevent the defect. 42 Pa.C.S.A. §§ 8321-8327; Burbage v. Boiler Engineering & Supply Co., 433 Pa. 319, 249 A.2d 563 (1969); Mixter v. Mack Trucks, Inc., 224 Pa.Superior Ct. 313, 308 A.2d 139 (1973). Indemnity, a common-law equitable remedy, shifts the entire loss from one defendant to another. Builders Supply Co. v. McCabe, 366 Pa. 322, 77 A.2d 368 (1951). Contribution is codified by statute, 42 Pa.C.S.A. §§ 8321-8327, and requires those who have liability of a concurrent character under the relevant tort law to share the loss equally. See Builders Supply Co. v. McCabe, supra; Globe Indemnity *457v. Agway Inc., 456 F.2d 472 (3rd Cir.1972). These remedies between defendants are available even against defendants whom the plaintiff does not sue, and their statute of limitations does not commence at the time of the plaintiffs injury. Wnek v. Boyle, 374 Pa. 27, 96 A.2d 857 (1953).3 Thus, victims may not, by the timing of their complaint, choose which tortfeasor will pay, and defendants faced with the frequent occurrence of eleventh-hour lawsuits may still pursue their rightful equitable remedies against other tort-feasors. Id.
Indemnity, as the more drastic remedy, is “recognized in cases where community opinion would consider that in justice the responsibility should rest upon one [defendant] rather than the other.” W. Prosser, Law of Torts 313 (4th ed. 1971) (quoted with approval Mixter v. Mack Trucks, Inc., supra). Thus, indemnity is only available from those who are primarily liable to those who are merely secondarily or vicariously liable. Builders Supply Co. v. McCabe, supra. To evaluate primary as against secondary liability courts have focused on factors such as active or passive negligence and knowledge of or opportunity to discover or prevent the harm. Id. In chain of distribution cases, where there are many levels of contact with the product, and thus several possible degrees of liability, our courts have cited with approval Restatement of Restitution § 95 (1936):
Where a person has become liable with another for harm caused to a third person because of his negligent failure to make safe a dangerous condition of land or chattels, which was created by the misconduct of the other or which, as between the two, it was the other’s duty to make safe, he is entitled to restitution from the *458other for expenditures properly made in the discharge of such liability.
See Mixter v. Mack Trucks, Inc., supra. The Restatement of Restitution also addresses indemnity in a chain of distribution case:
Where a person has supplied to another a chattel which because of the supplier’s negligence or other fault is dangerously defective for the use for which it is supplied and both have become liable in that to a third person injured by such use, the supplier is under a duty to indemnify the other for expenditures properly made in discharge of the claim of the third person, if the other used or disposed of the chattel in reliance upon the supplier’s case and if, as between the two, such a reliance was justifiable..
Restatement of Restitution § 93(1) (1936). When adapting these standards to strict liability cases, see Burbage v. Boiler Engineering & Supply Co., supra; Mixter v. Mack Trucks, Inc., supra, our courts look to the facts rather than the form of liability alone, id., and “view trade relations realistically rather than mythically.” Verge v. Ford Motor Co., 581 F.2d 384 (3rd Cir.1978).4 Thus, in determining who may be “primarily responsible” and required to indemnify in a products liability case, our courts have evaluated the facts in light of products liability policies, particularly by focusing on opportunity to discover or actual knowledge of the defective condition and on the relative burdens of cor*459recting or preventing the defect. Burbage v. Boiler Supply & Engineering Co., supra; Mixter v. Mack Trucks, Inc., supra; Verge v. Ford Motor Co., supra (relevant facts include trade custom, relative expertise, and practicality).5
Here, the jury’s verdict can only be fairly interpreted as awarding full indemnity to Sears from General Electric. Although Sears’ complaint, alleging that General Electric is “alone ... or jointly or severally liable or liable over,” sought either indemnity or contribution in the alternative, compare Globe Indemnity v. Agway, Inc., supra, the lower court’s jury instructions narrowed the issue to indemnity alone. “Sears has said that General Electric is the one liable.... [Djecide if between Sears ... and General Electric which of those do you think is responsible.” N.T. at 312. General Electric did not object, nor had it requested a point for charge on contribution. The jury’s verdict, although it did not mention indemnity or exclusive liability, compare Burbage v. Boiler Engineering & Supply Co., supra; Mixter v. Mack Trucks, Inc., supra, did find General Electric liable “in the case of Sears ... versus General Electric.” Verdict sheet. Thus, in light of the *460court’s instruction, the jury awarded indemnity to Sears. We must therefore determine, under General Electric’s contentions in post-trial motions and on appeal, whether the lower court acted within its discretion in finding the verdict of indemnity consistent with the weight of the evidence and in denying judgment n.o.v. See Yandrich v. Radic, supra (scope of review).
The non-party Roper Corporation designed, tested, and assembled this mower. General Electric had supplied the electrical system. A Roper design engineer testified that General Electric shared responsibility for safety features in the electrical system and could have vetoed the lack of a deadman’s switch. (N.T. February 6, 1979 at 235-36, 263-64). Although Sears marketed the mower under its brand-name and with an owner’s manual showing the defective design, no evidence indicated that Sears directly controlled the design or had available the expertise to evaluate its safety. See Verge v. Ford Motor Co., supra. In determining liability to consumers, courts have noted that the lack of a deadman’s switch on a lawnmower is an obvious design defect apparent to a non-manufacturer retailer, Daniels v. McDonough Power Equipment Inc., supra, and that the act of placing one’s name on a product is a factor in assessing responsibility because it frequently causes a product to be used in reliance upon the seller’s reputation, Restatement (Second) of Torts § 400. However, as between Sears, the non-manufacturer retailer, and General Electric, which was engaged in the manufacture and thus creation of the dangerous condition, this record supports the jury’s award of indemnity to Sears. Taking all facts and reasonable inferences in favor of the verdict, the jury could conclude that General Electric was primarily liable for the creation of the danger and that Sears, justifiably relying on its suppliers, was only secondarily liable. See Mixter v. Mack Trucks, Inc., supra; Restatement of Restitution §§ 93, 95. Thus, judgment n.o.v. was properly denied. Because the record is virtually devoid of evidence of Sears’ role in the design of this mower, other than the brandname *461and owner’s manual, upon reviewing all the evidence it is neither patently unreasonable nor shocking to the judicial conscience that the jury would place greater weight on the direct evidence of General Electric’s role in manufacturing the mower. Thus, the denial of a new trial because of the weight of the evidence was not an abuse of discretion. Accordingly, we are satisfied that this record supports the jury’s verdict of indemnity and the court’s judgment entered upon that verdict.
Affirmed.
WIEAND, J., files a dissenting opinion.. Sears’ contention that the court, before submitting a products liability case to the jury, is required to determine as a matter of law that the evidence supports a “duty” to provide a product with the missing safeguard mischaracterizes the factual nature of the determination of a defect and the court’s role as explained in Azzarello v. Black Bros. Co., supra.
. Other states permit "apportionment" in strict liability cases, that is submitting the question of relative responsibility to the factfinder in each case, as is done in comparative negligence. Daly v. General Motors Corp., 20 Cal.3d 725, 144 Cal.Rptr. 380, 575 P.2d 1162 (1978); Dole v. Dow Chemical Co., 30 N.Y.2d 143, 331 N.Y.S.2d 382, 282 N.E.2d 288 (1972); City of Franklin v. Badger Truck Sales, Inc., 58 Wis.2d 641, 207 N.W.2d 866 (1973). See Model Uniform Products Liability Act § 111 (U.S.Dept. of Commerce 1979); Comment, Apportionment between Partmakers and Assemblers in Strict Liability, 49 U.Chi.L.Rev. 544 (1982); Note, Another Look at Strict Liability: The Effect of Contribution Among Tortfeasors, 79 Dick.L.Rev. 125 (1974).
. Rather, the statute of limitations commences when judgment is entered against the defendant seeking indemnity or contribution. Id. The litigation of these claims before that judgment, as during the plaintiffs initial lawsuit, is, in effect, an action for declaratory judgment. See Kutner, Statutes of Limitations and actions for contribution or indemnity, 33 Okla.L.Rev. 203 (1980).
. Thus, a traditional verbal formulation is that indemnity is available to parties whose liability is "imputed or constructive only, being based on some positive rule of common or statutory law or because of a failure to discover or correct a defect or remedy a dangerous condition caused by the act of the one primarily responsible." Builders Supply Co. v. McCabe, supra 366 Pa. at 328, 77 A.2d at 371. Applied to landowners and employers who were vicariously liable for acts of builders on the land or employees who had actually created the danger, this test is compelling and easily applied. However, in a strict liability case all or several parties in the chain of distribution are held liable simply by a "rule of ... law." Id. Such liability, however, does not preclude the possibility of one defendant being negligent or more responsible in fact, under the scheme of the relevant products liability law, than other suppliers. See Mixter v. Mack Trucks, Inc., supra.
. As a matter of products liability law, Restatement (Second) of Torts § 402A left the questions of shifting or sharing liability among defendants to the subsequent development of case law. Id. Comment on Caveat p, q. The cases reveal various types of defects leading to varying allocations of liability. For injuries caused by malfunctioning components whose defective condition was hidden from subsequent assemblers and distributors, courts have required the component manufacturer to indemnify all other defendants. Burbage v. Boiler Engineering & Supply Co., supra; Mixter v. Mack Trucks, Inc., supra; Tromza v. Tecumseh Products Co., 378 F.2d 601 (3d Cir.1967). For defective designs attributable solely to the assembler of the finished product and not known to or within the control of other partmakers or suppliers, courts have required the assembler to bear the entire loss. See Taylor v. Paul O. Abbe, Inc., supra; Mayberry v. Akron-Rubber Machinery Corp., 483 F.Supp. 407 (N.D.Okla.1979). Finally, where the absence of a safety device or an obvious feature of design is the defect, courts make a closer examination of the relative roles and control over design of the various defendants, whether partmakers, assemblers, or subsequent distributors. Verge v. Ford Motor Co., supra; Ford Motor Co. v. Russell & Smith Ford Co., 474 S.W.2d 549 (Tex.Civ.App. 1971).