who can identify pitbull bites?

Pitbull dogs are as "ferocious" as any other dogs. Generally, that's as ferocious as they were trained to be, or as the situation warrants if the dog thinks it's alone and in a fight to the death.

So I'm going to address the question of bite severity first, and then ferocious attacks second.

Bite severity:
When looking at the results of a dog attack, there's no casual way to tell the breed of the dog - whether it's a pit bull, a Cocker Spaniel (which BTW, usually ranks very high in bite records), a Chihuahua, or a German Shepherd, unless you're a trained investigator who is doing measurements of bite width, hair analysis, etc. For instance, some photos (all photos of separate incidences):

Dog bite from German Shepherds: 

Dog bite from Aussie Shep/Lab mix:

Dog bites from a Pit bull or mix: 

A boxer bite:  

Shiba Inu bites:

Springer spaniel:

Etc., ad nauseum (sometimes, literally). So from the sample above, I'd say GSDs (large dogs) are pretty mild, and Shiba Inus (small dogs) are dangerous, maiming dogs. But again, this is just a *small sample*, showing that you can't really judge a bite to a breed.

So let's talk about severity of attacks:

Again, let's pull up some recent data for fatal attacks (which to me qualifies under ferocious), which shows that the research "...identified a significant co-occurrence of multiple potentially preventable factors."

From that link:
The co-occurring factors are potentially preventable
 
Based on an analysis of all DBRFs known to have occurred over a ten-year period, the researchers identified a striking co-occurrence of multiple, controllable factors:

• • no able-bodied person being present to intervene (87.1%);
• • the victim having no familiar relationship with the dog(s) (85.2%);
• • the dog(s) owner failing to neuter/spay the dog(s)(84.4%);
• • a victim’s compromised ability, whether based on age or physical condition, to manage their interactions with the dog(s) (77.4%);
• • the owner keeping dog(s) as resident dog(s), rather than as family pet(s) (76.2%);
• • the owner’s prior mismanagement of the dog(s) (37.5%);
• • the owner’s abuse or neglect of dog(s) (21.1%).

Four or more of these factors were present in 80.5% of the cases.

And:
Breed was not one of the factors identified   The authors report that the breed of the dog or dogs could not be reliably identified in more than 80% of cases. News accounts disagreed with each other and/or with animal control reports in a significant number of incidents, casting doubt on the reliability of breed attributions and more generally for using media reports as a primary source of data for scientific studies. In only 45 (18%) of the cases in this study could these researchers make a valid determination that the animal was a member of a distinct, recognized breed. Twenty different breeds, along with two known mixes, were identified in connection with those 45 incidents - See more at: Dog Bite-Related Fatalities

There are other studies put out about dog bite statistics every year, but beware of studies, and always look at the data. Make sure any study you read has a method of correctly identifying a dog, not just anecdotal or assumption.

An older study regarding dog bite fatalities:  Page on cdc.gov

But a few things in closing:

a) A larger dog, with more weight behind it, will typically do more damage than a small one. That's just physics for you.
b) Overall, dog bite statistics are trending upwards. More people are getting bitten and getting medical treatment. 
c) With the increase in legislation, urban living, and dogs kept increasingly as pets versus working dogs, today's dog is likely to be less socialized, both with humans and other animals, then forty years ago.

Any dog can be ferocious. It's up to the owner to properly house them, raise them, train them, socialize them. If you have an owner that doesn't do any of those, you have the potential for a vicious dog.

by Teleri Beaty,