In the context of criminal procedural law, the chain of custody emerges as a crucial mechanism for the integrity of evidence and is established by Law No. 13.964/2019, known as the Anti-Crime Package, seeking to regulate all procedures necessary to ensure that the evidence collected is preserved from its collection to its disposal, preventing its contamination or improper handling.

This concept has become a cornerstone for ensuring the integrity of evidence is maintained, which is fundamental for a transparent, fair, and evidence-based judicial process.

The chain of custody is one of the most critical elements in criminal and environmental investigations, guaranteeing the integrity of the evidence collected and ensuring that it can be used effectively in legal proceedings. 

In cases of environmental disasters and crimes, this chain takes on even greater importance, since it involves the preservation of evidence and samples that can determine the causes of the event and those responsible for its occurrence. Strict adherence to this process is essential to ensure that accountability occurs fairly and that environmental impacts are correctly assessed and mitigated.

The Concept of Chain of Custody

The chain of custody refers to the set of all procedures used to maintain and document the chronological history of evidence collected at crime scenes or from victims, to track its possession and handling from its identification to its disposal. It is an essential protocol to prevent contamination or manipulation of evidence, which could compromise the credibility of the investigation. 

Aury Lopes Jr. lists the chain of custody as a species from which different genera are derived:

It is important to consider that there will be different morphologies of the chain of custody depending on the type of evidence we are dealing with. A forensic DNA test, for example, has specific characteristics that require the establishment of a certain routine for collection, transport, storage, analysis, etc., which will be completely different from the forensic analysis of material obtained from a wiretap, for example.

In environmental crimes, proving chemical contamination, destruction of protected areas, or illegal dumping of waste requires rigorous control from collection to laboratory analysis. Any external interference can compromise not only the adulterated evidence but the entire investigative process of the criminal case.

In Brazil, criminal and environmental legislation imposes specific guidelines for maintaining the chain of custody. The Code of Criminal Procedure (CPP), amended by Law No. 13.964/2019, introduced detailed rules on the chain of custody, requiring meticulous records of each stage of the process, as well as the identification of all agents involved in handling the evidence.

Importance of the Chain of Custody in Environmental Crimes

Unlike traditional criminal investigations, environmental crimes present specific challenges related to the dispersal of evidence and the volatility of certain traces. For example, in cases of oil spills, water and soil contamination can spread rapidly, making the immediate collection of samples for laboratory analysis essential.

Furthermore, environmental investigations often involve a diverse range of actors, including public agencies such as the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA), the Federal Police, environmental experts, and academic researchers. The involvement of multiple entities makes maintaining an accurate record of each piece of evidence collected even more important, preventing disputes about its origin.

In addition to this, in cases of environmental disasters with immediate victims, as was the case in Brumadinho, while rescuing victims is underway, forensic investigations are conducted to avoid losing the opportunity to produce evidence.

Stages of the Chain of Custody

The chain of custody follows a standardized flow of protocols, aiming to safeguard the evidence produced, ensuring it is not altered or lost. In legal doctrine, the stages of the chain of custody can be further divided, creating ramifications of the same process. For example, Professor Aury establishes 10 (ten) stages. For the purposes of this work, in order to simplify the understanding of this process, we believe that the chain of custody can be divided into six main stages: collection, preservation, storage, transport, presentation of evidence, and disposal. Each of these phases is fundamental to guaranteeing the validity of the examined material.

Evidence Collection

Collection must be meticulous, following specific protocols for each type of evidence. In environmental crimes, the main materials collected include samples of water, soil, air, vegetation, and impacted fauna. Collection must be carried out with appropriate equipment, and documentation must be detailed, recording the location, date, and environmental conditions at the time of seizure.

Preservation of Evidence

After collection, samples need to be properly preserved to prevent degradation. The integrity of the material can be compromised by factors such as exposure to heat, humidity, or chemical agents. Storage in sealed, labeled containers with proper temperature control is essential to ensure that the evidence retains its original characteristics.

Storage and Control

The storage phase requires strict control to prevent unauthorized access and tampering with the samples. Laboratories and responsible agencies must maintain records of sample entry and exit, ensuring that any movement is documented and justified.

Safe Transport

The movement of evidence between collection, storage, and laboratory analysis locations must be carried out safely, using specific packaging and controlled transport. Any change in the ownership of the evidence must be recorded to ensure its traceability.

Presentation in Legal Proceedings

Evidence must be presented in court proceedings in a transparent manner, with complete documentation and expert reports attesting to the authenticity of the evidence analyzed. The chain of custody must be clearly demonstrated to avoid challenges from the defendants' legal team.

Discard

Finally, after the proper use and presentation of the evidence, the release of the trace material must occur, respecting current legislation and, when pertinent, with judicial authorization.

Challenges in Maintaining the Chain of Custody in Environmental Disasters

In cases of large-scale environmental disasters, such as dam breaks, forest fires, or chemical spills, the chain of custody faces additional challenges. The extent of the damage, the difficulty of accessing some areas, the high cost, and the need for a rapid response can compromise the collection and preservation of evidence.

Furthermore, human interference can affect the credibility of investigations. Companies responsible for impactful activities may attempt to hinder the gathering of evidence, whether through the removal of documents, falsification of records, or secondary contamination of the affected area. Therefore, it is essential that regulatory bodies have sufficient autonomy and resources to act independently and with technical rigor.

Another significant obstacle is the need for cooperation between different entities involved in the investigative process. Often, forensic examinations are conducted by different institutions, and a lack of communication can result in the loss or contamination of evidence.

Technologies and Methods to Improve the Chain of Custody

Technological advancements have enabled the improvement of methods for preserving and tracking environmental evidence. The use of blockchain, for example, has been studied as an effective tool to guarantee the authenticity of records, allowing for the monitoring of each stage of the chain of custody in an inviolable manner.

Furthermore, drones and satellite imagery have been used to map affected areas, record the situation before evidence removal, and accurately document the environmental impact. Evidence management software also assists in organizing and tracking samples, reducing human error and ensuring greater reliability in the investigative process.

Conclusion

The chain of custody plays a crucial role in the investigation of environmental disasters and crimes, ensuring that the evidence collected is kept intact and can be used effectively in legal proceedings. The correct application of this procedure not only strengthens the accountability of those responsible for environmental damage, but also contributes to the implementation of stricter environmental protection policies.

Given the challenges faced, it is essential that regulatory bodies and investigators adopt modern and rigorous practices, ensuring that the chain of custody is respected at all stages of the investigation. The use of innovative technologies and the continuous training of the professionals involved can be key to ensuring that environmental justice is effective and that the environment is protected for future generations.