(dissenting, with whom Lynch, J., joins). I agree that the plaintiff’s proffered testimony “that the porch rail in question was loose approximately two months before the date of the accident” should have been admitted. That testimony, together with the property manager’s and carpenter’s testimony that the railing had not been repaired during that two-month period, was relevant because it would have tended to show that at the time of the accident the railing was “loose.” However, as the court recognizes, ante at 47-48 & n.4, the erroneous exclusion of evidence does not justify the award to a new trial unless the error “injuriously affected the substantial rights of the parties.”
*51The erroneous exclusion of the evidence tending to prove the looseness of the railing did not injuriously affect the substantial rights of either party. The error was harmless. In reaching the opposite conclusion, the court reasons that the jury may have found the defendant negligent on the ground that she maintained a railing with a defective condition, other than looseness, that was unrelated to the accident. If the excluded evidence had been admitted, the court theorizes, the jury might have found that the defendant’s maintenance of a railing that was loose constituted negligence and that that condition caused or contributed to cause the accident.1
The court’s reasoning is flawed. The plaintiff had the burden to prove by the fair weight or preponderance of the evidence that the defendant’s negligence caused, at least in part, the child’s injuries. “After the evidence has been weighed, that proposition is proved by a preponderance of the evidence if it is made to appear more likely or probable in the sense that actual belief in its truth, derived from the evidence, exists in the mind or minds of the tribunal notwithstanding any doubts that may still linger there” (citations omitted). Sargent v. Massachusetts Accident Co., 307 Mass. 246, 250 (1940). See Stepakoff v. Kantar, 393 Mass. 836, 843 (1985). There was no evidence, either admitted or proffered, that would have warranted a finding, in keeping with that standard, that the child fell from the porch because of a loose railing. The evidence together with the proof that was offered but excluded, leaves to conjecture the cause of the fall. The fall occurred while the child “stood on the bottom section of the railing, and looked down at some youngsters.” Ante at 46. Common experience does not teach that, in such circumstances, the child would be unlikely to have fallen were it not for an undefined, perhaps miniscule, degree of looseness of the railing.
The defendant moved for a directed verdict. Had the excluded evidence been admitted, the proffered evidence to*52gether with all the other evidence in the case would not have warranted the jury in finding that looseness of the railing played any role in the accident. Thus, even if the judge had not erred, the defendant would have been entitled to the allowance of her motion. Therefore, the erroneous exclusion of the proffered evidence did not injuriously affect the plaintiff’s substantial rights (nor, of course, the defendant’s). I would affirm the judgment below.
The court states, ante at 50, that “[i]f the jury had found that same railing was also loose and shaky, perhaps they would have further found that the defendant’s negligence was the proximate cause of the child’s fall.” There is no evidence in the record that the railing was “shaky.”