Slavery or Servitude
Slavery is described as the status or condition of a person over whom any or all of the powers attaching the right of ownership are exercised. In essence, characteristics of ownership need to be present for a state of slavery to exist.
Servitude is a linked but much broader term than slavery. It includes, in addition to the obligation to provide certain services to another, the obligation on the "serf" to live on the other's property and the impossibility of changing his status".
Forced or Compulsory Labour
The ECHR, in the case of Van der Mussele affirmed that the International Labour Organisation (ILO) conventions were the starting point for interpreting Article 4. The conventions defined forced or compulsory labour as being "all work or service which is exacted from any person under the menace of any penalty and for which the said person has not offered himself voluntarily".
Domestic Case Law
The case of William Connors and others  offers some further guidance on the distinction between these 3 elements. This case involved a family who, cajoled, bullied and through deception, recruited vulnerable men to work for them. The men worked long hours in very poor conditions 7 days a week, whilst being subjected to violence, threats and abuse. A manifestation of this control was that many of the victims were deprived of the will to leave; others were too demoralised to do so. All five defendants were convicted of a single count of conspiracy to require a person to perform forced or compulsory labour. During the course of the trial, the judge directed the jury to acquit the defendants of conspiracy to hold a person in slavery or servitude. The trial judge had commented that in order for servitude to be established, a court must find that it was impossible for the workers to change their status.