In the Bianca Jones case -
No they kept on seeing her alive. There seemed to be so many closely related children involved I don't know if that person knew exactly who they were looking at.
There was a lot more to the Bianca Jones case than people are making out. The killer was not just convicted because of the dogs alone. There was a great deal of circumstantial evidence ( of which the dog alerts were included) and the witnesses who supposedly saw her alive afterwards were deemed unreliable for various reasons.
DiAndre Lane admitted beating her that night and early morning, he had a 2 feet long stick that he had made especially for beating his kids. His girlfriend heard 'screams' as he was doing it. He felt the need to admit that after the beating, Bianca 'fell and banged her head' and he hit her more to keep her awake in case she fell unconscious. In the morning he put her in the car seat and his other kids said she was 'silent with a blanket over he face'. One of the other kids also testified about her fathers violence and injuries she was caused by having clothing stuffed in her mouth whilst being beaten. Then she disappeared in a 45 minute period that Lane could not account for.
The dogs methods and training was supported in court by Rex Stockham who was in charge of canine training at the FBI. The court was satisfied that training was sufficient and the methods used meant the evidence could be admitted. Stockham was a forensic scientist and he wrote various peer reviewed papers on dog training.
https://caselaw.findlaw.com/mi-court-of-appeals/1683760.html"At trial, FBI Canine Program Manager Rex Stockham testified as an expert in forensic canine operation. Stockham testified about the process of training and testing victim recovery dogs. Stockham's protocol called for regular single-and double-blind testing of dogs throughout their working lives. Stockham's program had three full-time handlers in its program, including Martin Grime. Stockham testified that he had tested Morse and Keela, Grime's dogs, and that both dogs had accuracy ratings in the high 90 percent range. Stockham testified that dogs have been able to smell the odor of decomposition as soon as 2 hours after a victim's death, or years after a victim's burial.
Grime testified as an expert in the training and employment of cadaver dogs. According to Grime, he is a full-time contractor for the FBI. Grime worked with Morse, a dog “trained to search for and detect the odor of decomposing human remains,” and Keela, “trained to search for and locate specifically human blood.” Grime testified that there was no methodology to test the dogs' responses when there is no recoverable material, and that the odor of decomposition may transfer if a person touches a dead body and then touches something else.
According to Grime, on December 4, 2011, he took his dogs to an enclosed warehouse that contained 31 vehicles. Grime was told that Bianca was in one of the vehicles at the time of the carjacking, but was not told which vehicle was involved. Morse alerted Grime to the presence of the odor of decomposition in the back seat and trunk of a silver Grand Marquis. Keela later screened the car and did not alert Grime to the presence of human blood.
Grime testified that, after the vehicle screening, he took the dogs to an administrative building to screen the items removed from Dungey's car. Grime did not know where the objects were located in the building, and the objects had been placed in a room filled with “all sorts of things.” Morse alerted Grime to the odor of decomposition in Bianca's car seat and a bag containing Bianca's blanket. Grime later took the dogs to Dungey's house. Morse alerted him to the odor of decomposition in a room that contained bunk beds and a closet without a door."
"......In Norwood, this Court held that tracking dog evidence is sufficiently reliable if the proponent of the evidence shows four things:
(1) the handler was qualified to use the dog; (2) the dog was trained and accurate in tracking humans; (3) the dog was placed on the trail where circumstances indicate the alleged guilty party to have been; and, (4) the trail had not become so stale or contaminated as to be beyond the dog's competency to follow it. [16 ]
We reject Lane's argument that, because chemical evidence cannot corroborate whether there was decomposition at the locations Morse identified in this case, the evidence must be excluded as unreliable. Clearly, the four-part test adopted by this Court to ensure the reliability of tracking dog evidence does not exactly correlate to the use of cadaver dogs. However, cadaver dog evidence is not significantly different from other forms of tracking dog evidence. Tracking dogs and cadaver dogs both use a precise sense of smell to identify scents that are outside the range of human ability to detect. Scientific devices can no more follow the scent left on a piece of discarded clothing from the scene of a robbery to a person's home than they can identify the smell of decomposing human remains. Just as it is not a reason to exclude all tracking dog evidence, the lack of scientific verification of the presence of a specific scent is not a reason to exclude cadaver dog evidence in a blanket fashion. We conclude that the trial court must instead consider the reliability of the cadaver dog evidence in each case."
So I don't think the dog evidence was relied on too heavily, or included in the trial without thorough assessment.
D'Andre Lane was proven to be a habitual abuser of his kids and a liar. The dog evidence supports that he lied and that Bianca died as the result of his abuse. In this case Rex Stockam estimated the dogs of having a 90% + accuracy rate , the dog evidence was taken on a case by case basis depending on the accuracy of the training methods and other factors. I don't see any reason why this could not be done in the McCann case.