A more thorough explanation:

Definition: A critical stage is a point in a criminal prosecution where the accused's rights or defenses may be affected by the absence of legal representation. This triggers the accused's right to appointed counsel under the Sixth Amendment. Examples of critical stages include:

• Preliminary hearings
• Jury selection
• Trial

These examples illustrate that at each of these stages, the accused's rights and defenses may be impacted if they do not have legal representation. For example, at a preliminary hearing, the accused may be required to enter a plea or have evidence presented against them. Without legal representation, they may not understand their options or be able to effectively challenge the evidence. Similarly, during jury selection, the accused's legal team may need to challenge potential jurors who may be biased against them. Without legal representation, the accused may not be able to identify these biases or challenge them effectively.