the lid of the machine is put down, the safety switch by reason of the pressure of the lid is put into a “down” position which completes the electric circuit causing the tub to spin.
The evidence shows that Mrs. Friedman opened the lid of the washing machine to take out her washing. This fact we believe to be uncontroverted. But thereafter the positions of the parties sharply diverge. The plaintiffs’ position is stated, we conclude, by their counsel in his summation to the jury and is as follows: "This washing machine has a feature built into it, that the manufacturer brags about and rightly so, and that is this safety device that says when the top is open — it says it in the book, it says it right on the lid [of the machine] to make sure you know about it — when the top is open, it can’t spin, and the fact is that in this case with the top open, it did spin, and nobody questions that.
» * “[I]f everything is working right it [the washer] can’t spin with the lid open, and in order for it to spin with the lid open, something has to be wrong.
# “There has to be a defect, and this defect makes this machine unreasonably dangerous because you can get your hand or thumb caught in it and get it torn Q-f-jj »
The Friedmans point out that there was evidence that the safety switch connection was “gummed up” with residue of soap, “slime” or “sludge”, and when the safety switch was pressed into its down position, this gum-like substance and, perhaps, its accompanying moisture, caused the inner mechanism [micro-switch] to stick and may have aided in closing the circuit.2
It will be observed that the plaintiffs did not assert that the position of the safety switch was unreasonably dangerous because it could be touched by someone putting clothes into or taking clothes out of the washing machine.
It is the theory of General Motors that reaching inside the machine to withdraw her washing, Mrs. Friedman touched the "Safety Switch” in such a way that the tub was actuated into its spinning cycle. Dr. Fegley, the defendant’s expert, gave opinion evidence as to how Mrs. Friedman could have been injured, stating: “[I]f Mrs. Friedman had opened the lid to the washing machine during the middle of the spin cycle and then reached in and put her hand on the lid safety switch, this would have started to spin again.” Dr. Fegley’s statement is not entirely clear but we take it to mean that in his opinion if Mrs. Friedman had put her hand on the lid safety switch, the spin cycle would have started again. This reply was given in answer to a question as to what was the opinion of Dr. Fegley as to the cause of the accident.3
2
The court charged in respect to this issue, viz., the accumulation of slime and sludge: “[I]f you accept this as correct, namely, that the design of the washer was improper in that it was designed in such a way as to permit the accumulation of slime and sludge in such a way as to render this safety switch likely to become unsafe, if that is your conclusion, you would have the right to conclude that this condition, this design condition, certainly existed when the washer was sold, and the mere fact that the accident didn’t happen until some time thereafter would not prevent you from concluding that the accident was due to a defective condition which was existing in the washer at the time it was sold.” The jury obviously concluded that there was no defect in the design of the washing machine in this respect.
3
The plaintiffs assert that the court below committed prejudicial error in not striking from the record the testimony of defendant’s expert, Dr. Fegley, who gave opinion evidence as to how Mrs. Friedman could have been injured. The plaintiffs contend that this statement is mere “conjecture” and is not based on any evidence. But Dr. Fegley had testified at some length respecting the construction and operation of the machine and had tested it, albeit two and a half years after the accident. While there was no direct evidence that Mrs. Friedman had put her *536hand on the lid safety switch, the evidence shows that she could have done so however inadvertently. We cannot say that Dr. Fegley’s statement was more conjecture. It was opinion evidence based on the nature of the machine and its operation. His testimony meets the tost laid down by us in Arnold v. Loose, 352 F.2d 959, 963, (3 Cir. 1965) for it is the opinion of an expert based on material facts which are part of the record.