The terrier must present a lively, active and alert appearance. It should impress with its fearless and happy disposition. It should be remembered that the Jack Russell is a working terrier and should retain these instincts. Nervousness, cowardice or over-aggressiveness should be discouraged and it should always appear confident.
A sturdy, tough terrier, very much on its toes all the time, measuring between 10″ and 15″ at the withers. The body length must be in proportion to the height, and it should present a compact, balanced image, always being in solid, hard condition.
Should be well balanced and in proportion to the body. The skull should be flat, of moderate width at the ears, narrowing to the eyes. There should be a defined stop but not overpronounced. The length of the muzzle from the nose to the stop should be slightly shorter than the distance from the stop to the occiput. The nose should be black. The jaw should be powerful and well boned with strongly muscled cheeks.
Should be almond shaped, dark in color and full of life and intelligence.
Small “V” shaped drop ears carried forward close to the head and of moderate thickness.
Strong teeth with the top slightly overlapping the lower.
The left two bites are acceptable; the far left bite is preferred.
Clean and muscular, of good length, gradually widening at the shoulders.
The shoulders should be sloping and well laid back, fine at points and clearly cut at the withers. Forelegs should be strong and straight boned with joints in correct alignment. Elbows hanging perpendicular to the body and working free of the sides.
The chest should be shallow, narrow and the front legs not too widely apart, giving an athletic, rather than heavily chested appearance. As a guide only, the chest should be small enough to be easily spanned behind the shoulders, by average sized hands, when the terrier is in a fit, working condition. The back should be strong, straight and, in comparison to the height of the terrier, give a balanced image. The loin should be slightly arched.
Should be strong and muscular, well put together with good angulation and bend of stifle, giving plenty of drive and propulsion. Looking from behind, the hocks must be straight.
Round, hard padded, wide, of cat-like appearance, neither turning in nor out.
Should be set rather high, carried gaily and in proportion to body length, usually about four inches long, providing a good hand-hold.
Smooth, without being so sparse as not to provide a certain amount of protection from the elements and undergrowth. Rough or broken coated, without being woolly.
White should predominate (i.e., must be more than 51% white) with tan, black, or brown markings. Brindle markings are unacceptable.
Movement should be free, lively, well coordinated with straight action in front and behind.
Old scars or injuries, the result of work or accident, should not be allowed to prejudice a terrier’s chance in the show ring unless they interfere with its movement or with its utility for work or stud.
A Jack Russell Terrier should not show any strong characteristics of another breed.
Shyness, Disinterest, Overly aggressive, Defects in bite, Weak jaws, Fleshy ears, Down at the shoulder, Barrel ribs, Out at elbow, Narrow hips, Straight stifles, Weak feet, Sluggish or unsound movement, Dishing, Plaiting, Toeing, Silky or woolly coats, Too much color (less than 51% white), Shrill or weak voice, Lack of muscle or skin tone, Lack of stamina or lung reserve, Evidence of foreign blood
Thanks to Jack Russell Terrier Club of America