Lawyer is a typical example of service sector. Not only lawyer but all personnel in the field of service sector belong to this group. The term tertiary production is a bit awkward, as in fact tertiary economy is technically away from production anyway. The following extract from wikipedia may give you a little insight.
The tertiary sector of the economy (also known as the service sector or the service industry) is one of the three economic sectors, the others being the secondary sector (approximately manufacturing) and the primary sector (extraction such as mining, agriculture and fishing). The general definition of the tertiary sector is producing a service instead of just an end product, in the case of the secondary sector. Sometimes an additional sector, the "quaternary sector", is defined for the sharing of information (which normally belongs to the tertiary sector).
Increasingly service sector businesses need to focus on this idea of the “knowledge economy”. They need to keep ahead of competitors by understanding what it is their customers want and be in a position to deliver this quickly and efficiently.
One good example of this is the banking industry which has gone through enormous changes in recent years. Using information and communication technology, banks have vastly reduced the number of staff they need. Many banks and building societies have merged to form much “leaner” businesses capable of extracting more profit from a wider customer base. The key to this process is gaining information about their customers and constantly communicating new products to them.