Norman Macdonald was heard at Tarbert on 13 June 1883. He is quoted as being a 50-year old crofter from the island of Scarp, which lies just off the northwest coast of Harris. Unfortunately, none of the 19th century censuses for Scotland mention anyone as being specifically from this island. It appears to be grouped under North Harris. Looking for a nearby township on mainland Harris, Govig, shows this to be included in enumeration district 6.
Only the 1901 census gives a break-down of the population of Scarp (172 people), and thus we can locate a Norman Macdonald who appears to match the description of the witness giving evidence to Lord Napier's Commission 18 years before. For reference, Scarp is listed as enumeration district 7 under registration district 111/1, with 200 residents.
He is listed as a cottar at 3 Scarp, aged 72. Norman is married to Ann, aged 60 in 1901, with four children: two sons who are fishermen: Kenneth, (25) and Donald John (22); and two daughters, both marked as scrot [domestic] Mary (19) and Marion (17).
Working back with this information, we do find Norman in the 1881 census as a fisherman, married to Ann (aged 39), with children Angus (8), Kenneth (7), Donald John (4) and Mary, 3 months.
By 1891, Norman is marked as a retired fisherman, aged 56. A new addition to the family is Marion, aged 7.
From his death certificate, we find confirmation that Norman Macdonald, a fisherman from Scarp, was married to Ann Macdonald MS Macinnes. His parents are named as Donald and Margaret Macdonald. Norman passed away on 21 August 1903 at the age of 74. The cause of his death is listed as rheumatism and valvular disease of the heart.
EDIT: Inclusion of additional census information from 1881, as per suggestion from Direcleit in comment below.