e-Government
Electronic administrative files, e-signatures, registries and electronic notifications.
Expert witness · IT & Telecommunications
Solid technical evidence for court and out-of-court proceedings
I am a qualified engineer and chartered expert witness. I prepare IT and telecommunications expert reports with methodological rigour, written in language that judges and lawyers can follow.
- Computer and Telecommunications Engineer
- Chartered and court-appointed expert
- Catalonia and all of Spain · CA / ES / EN
Expert services
Two degrees, one point of contact: I can cover both the IT and the communications side of the same case.
01Information technology
Digital evidence
Authenticity and integrity of emails, WhatsApp and other messaging apps, social media, documents and files.
Learn more →Digital forensics
Acquisition and analysis of computers, mobile phones and storage media, with chain of custody and hashing.
Learn more →Software & IT projects
Breach of contract, software defects, delays, ownership and copying of source code.
Learn more →ICT asset valuation
Valuation of applications, software and equipment: in-kind capital contributions, inheritances, liquidations and transactions.
Learn more →Cybersecurity & incidents
Unauthorised access, data breaches, ransomware, computer fraud and identity theft.
Learn more →02Telecommunications
Networks & circuits
MPLS circuits, leased lines and fibre access: availability, performance and SLA compliance.
Learn more →Carrier services
Service outages, number porting, billing and contracts with telecom operators.
Learn more →Telephony & communications
Analysis of call and SMS records, PBX systems and voice communications.
Learn more →Networks & coverage
LAN and Wi-Fi networks, structured cabling and coverage quality.
Learn more →03Cross-cutting
Rebuttal reports
Technical review of the opposing party's expert reports to identify errors and weaknesses.
Court testimony
Defending the report before the court, in Catalan, Spanish or English.
Preliminary advice
Assessing the technical viability of a case before proceedings begin.
Who I work for
- Lawyers & law firmsTechnical support for your litigation strategy.
- CompaniesDisputes with suppliers, employees or customers.
- IndividualsDigital evidence in civil, employment or criminal matters.
- Courts & public bodiesCourt appointments and official expert reports.
- InsurersClaims with a technology component.
How I work
- 01
Initial enquiry
You tell me about the case and I let you know, free of charge, whether there is a technical basis for a report.
- 02
Quote
You receive a fixed or phased quote with clear scope and timelines.
- 03
Evidence preservation
Acquisition with forensic tools, hashing and a documented chain of custody.
- 04
Expert report
A clear, reasoned and reproducible report, in line with art. 335 et seq. of the Spanish Civil Procedure Act.
- 05
Court testimony
I defend the report in court and answer questions from the parties and the judge.
About me
My name is Mario Pareja Nieto. I am a Computer Engineer and a Telecommunications Engineer (holding both the full and the technical engineering degrees in each field), registered with the Catalan professional associations COEINF and COETIC. I also hold a degree in Market Research and Techniques and several master's degrees in networks, ICT management and cybersecurity.
I work as an expert witness for courts in Catalonia and for lawyers, companies and individuals. I have first-hand experience of the corporate telecommunications sector (MPLS circuits and leased lines), which helps me understand cases from the inside. I am also a consumer arbitrator for IT matters at the Catalan Consumer Agency (Agència Catalana del Consum).
I work throughout Spain, mainly in Catalonia, and write reports in Catalan, Spanish or English.
Frequently asked questions
What is the difference between a party-appointed and a court-appointed expert?
A party-appointed expert is commissioned by one party and the report is filed with the claim or defence. A court-appointed expert is designated by the court. In both cases the expert must act objectively and may be questioned by all parties.
Is a WhatsApp screenshot valid evidence?
It may be accepted if the other party does not challenge it. If it is challenged, an expert report establishing the authenticity and integrity of the conversation from the device will usually be needed.
How much does an IT expert report cost?
It depends on the scope: number of devices, volume of data, urgency and whether court testimony is required. After the free initial enquiry you will receive a fixed quote.
How long does a report take?
A simple case can be ready in one or two weeks. If there are court deadlines, mention them in your enquiry so we can plan accordingly.
Do you work outside Catalonia?
Yes. I work throughout Spain, mainly in Catalonia. Much of the work can be done remotely, and testimony can be given by videoconference where the court allows it.
Which languages can the report be written in?
Catalan, Spanish or English.
Guides & resources
Practical articles on digital evidence and IT expert reports in Spain.
How to submit WhatsApp messages as evidence in Spanish courts
Screenshots, notarial records or an expert report: what works and what doesn't when submitting WhatsApp conversations as evidence in Spain.
Read the guide →Digital chain of custody: what it is and why it can make or break your evidence
What the chain of custody for digital evidence is, how it is documented with hash functions, and which mistakes can lead a court to reject evidence.
Read the guide →When you need an IT expert witness in Spain and how to choose one
Party-appointed or court-appointed expert, when to commission an IT expert report and what to check before hiring an expert witness in Spain.
Read the guide →Contact
Briefly describe your case. I will reply within 48 working hours.
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